I make a lot of sandwiches in my kitchen, but this Chicken Florentine Panini is one I come back to when I want something that feels special without a lot of fuss. It manages to be bright, savory, and comfortably melty all at once: balsamic-sweet onions, garlicky mayo, shredded spinach, thin chicken, and provolone pressed into a crisp, golden crust.

There are a few small techniques here that change the whole outcome — squeezing the spinach, flattening the chicken, and letting the crust cool so it crisps instead of collapsing. None are hard. They just pay off, and they turn familiar pantry items into a sandwich that actually competes with a café.

If you like sandwiches that are layered and intentional rather than thrown together, you’ll appreciate the order and timing in this recipe. It’s designed for weekday dinners or a relaxed weekend lunch, and it scales cleanly if you want to make more than two sandwiches.

Ingredient Notes

This recipe balances texture and flavor: a soft built-in crust becomes the sandwich exterior, while the fillings add moisture, tang, and melt. Read the notes below so you know which steps protect that balance — especially with the spinach and the baked crust.

Ingredients

1/4 cup mayonnaise — base for the garlicky spread; keeps the top layer moist and helps glue the sandwich together.
1 garlic clove, minced — adds punch to the mayo; mince finely so it disperses evenly.
1 (10-ounce) tube refrigerated pizza crust — foundation for the sandwich exterior; baking it first gives structure and crunch.
1 1/2 tablespoons olive oil, divided — for sautéing onions and cooking chicken; keeps things from sticking and adds flavor.
1 medium red onion, cut in half and thinly sliced — caramelizes quickly with sugar and balsamic; provides sweet-tangy contrast.
2 teaspoons granulated sugar — helps the onion caramelize and balance the vinegar.
1 tablespoon balsamic vinegar — bright acidity for the onions; don’t skip it.
1/4 teaspoon crushed red pepper flakes — a touch of heat to offset the richness.
2 boneless, skinless chicken breasts — flattened and quickly seared for even cooking and easy slicing.
salt and pepper — season simply; salt is essential to lift the flavors.
1/4 teaspoon dried thyme — a subtle herb note on the chicken that plays well with provolone.
1 (9-ounce) package frozen, chopped spinach, thawed and squeezed to get rid of liquid — concentrated green flavor; squeezing removes water so the sandwich doesn’t get soggy.
8 provolone cheese slices — melts smoothly and has mild flavor so it doesn’t overpower the other components.

Method: Chicken Florentine Panini

In a small bowl, stir together 1/4 cup mayonnaise and the minced garlic. Cover and refrigerate until assembly.
Preheat oven to 375°F.
While the oven preheats, heat 1 tablespoon olive oil in a large nonstick skillet over medium heat. Add the thinly sliced red onion and sauté 3 minutes. Add 2 teaspoons granulated sugar, 1 tablespoon balsamic vinegar, and 1/4 teaspoon crushed red pepper flakes; continue sautéing about 5 minutes, until the onions are softened. Transfer the onions to a bowl and wipe the skillet clean.
Unroll the 10-ounce refrigerated pizza crust into a 15×10-inch jellyroll pan and press to fit the pan. Bake in the preheated oven for 10 minutes. Remove and let cool, then cut the baked crust into 4 equal rectangles.
While the crust cools, prepare the chicken: flatten the two boneless, skinless chicken breasts to about 1/4-inch thickness with a meat mallet or rolling pin. Season both sides with salt, pepper, and 1/4 teaspoon dried thyme.
Heat the remaining 1/2 tablespoon olive oil in the wiped-clean skillet over medium-high heat. Add the flattened chicken and cook 4 to 5 minutes per side, until cooked through. Transfer the chicken to a cutting board, let rest 5 minutes, then slice.
Make sure the 9-ounce package of frozen chopped spinach is thawed and well squeezed to remove excess liquid.
To assemble 2 sandwiches: spread the mayonnaise mixture on one side of 2 of the crust rectangles. On the other 2 rectangles, divide and layer the sliced chicken, the squeezed spinach, and the cooked onions. Divide the 8 provolone slices evenly and place them on top of the fillings. Place the mayonnaise-spread rectangles on top of each sandwich, mayonnaise side down.
Lightly grease a cast-iron skillet with a thin coating of olive oil (use any oil remaining in the chicken skillet if available). Heat the skillet over medium-high. Add the sandwiches and cook until the bottoms are golden brown, pressing down gently with a spatula. Flip the sandwiches and cook until the second side is golden brown.
Remove sandwiches from the skillet, cut each sandwich in half, and serve.

Why This Recipe Is Reliable

Reliability comes from a few deliberate tweaks. Baking the refrigerated pizza crust before assembly prevents a raw, doughy interior and gives a sturdy surface that crisps when pan-fried. Flattening the chicken ensures quick, even cooking so you don’t end up with an overcooked exterior and raw center.

Squeezing the thawed spinach removes excess moisture that would otherwise make the sandwich soggy—once that water is out, the spinach adds concentrated flavor and green color without diluting the sauce or softening the crust. The quick-sautéed red onions build sweetness and a little tang from the balsamic, which balances the rich mayo and cheese.

The timing is forgiving: cook the onions and chicken while the crust bakes and cools. That keeps active hands to a minimum and prevents any one element from sitting too long and losing texture.

Swap Guide

Want to tweak texture or flavor? Here are targeted swaps that keep the structure intact:

Cheese — If you prefer a sharper melt, swap provolone for a mild sharp cheddar or fontina. Avoid crumbly cheeses that won’t create the same melt.
Bread base — If you don’t have a refrigerated pizza crust, a sturdy flatbread or thick focaccia sliced into rectangles will work. Toast it first to mimic the baked crust’s structure.
Onions — Yellow or sweet onions can replace red; they caramelize similarly with sugar and balsamic.
Fat for cooking — Use butter instead of some olive oil for a deeper flavor in the skillet, but keep the quantity moderate to avoid smoking.

Tools of the Trade

A few simple tools make this recipe easy and consistent:

Jellyroll pan (15×10-inch) — for baking and shaping the crust.
Meat mallet or rolling pin — to flatten the chicken breasts to an even 1/4-inch thickness.
Large nonstick skillet — for sautéing onions and cooking chicken without sticking.
Cast-iron skillet — for pressing and browning the assembled sandwiches; it holds heat and gives an even crust.
Small bowl and spoon — for the mayo-garlic mix.

Missteps & Fixes

Onions too sharp or undercooked

If the onions taste raw, cook them a few minutes longer with a splash of water to deglaze and soften. If they’re bitter, a pinch more sugar will round them out.

Soggy sandwich

Usually from un-squeezed spinach or a crust that wasn’t baked fully. Squeeze the thawed spinach in a towel until mostly dry. If your crust is soft when assembling, pop it back into a 350°F oven for 3–4 minutes to crisp before building the sandwich.

Chicken overcooked or rubbery

That happens when breasts are too thick. Take time to flatten to 1/4 inch and cook 4–5 minutes per side over medium-high. If the pan is too hot, reduce heat slightly so the outside browns without drying the meat.

Cheese not melting

Cover the skillet briefly for 30–60 seconds after flipping to trap heat and encourage melting. A slightly lower heat and short cover beats high heat that burns the crust before the cheese melts.

Dietary Swaps & Alternatives

If you need dietary adjustments, here are practical alternatives that preserve the sandwich’s integrity:

For lower fat, use a light mayonnaise and a lower-fat cheese. Expect slightly less richness but similar structure.
To reduce sodium, go lighter on added salt and choose a low-sodium cheese. Taste the fillings before adding extra salt.
Make it gluten-free by using a store-bought gluten-free pizza crust or flatbread; bake it fully and treat it the same as the crust in this recipe.
For a vegetarian option, replace the chicken with sliced, seasoned and grilled portobello or eggplant rounds, prepared to the same thickness.

Testing Timeline

I test these sandwiches in small batches to make sure timing fits a real home kitchen. Here’s a typical timeline that fits under 45 minutes from start to finish:

0:00–0:02 — Mix mayo and garlic and chill.
0:02–0:08 — Preheat oven and slice onions; begin sautéing onions.
0:08–0:18 — Bake the pizza crust for 10 minutes; finish onions in skillet.
0:18–0:22 — Remove crust, let cool; prep and flatten chicken.
0:22–0:30 — Cook chicken in skillet and let rest.
0:30–0:35 — Squeeze spinach and assemble sandwiches.
0:35–0:40 — Pan-fry sandwiches until golden and cheese is melted.

Store, Freeze & Reheat

Store any leftover assembled fillings (without the crust) in an airtight container in the refrigerator for up to 3 days. The baked crusts keep separately in a zip bag at room temperature for about 24 hours; after that they start to soften.

To reheat a made sandwich, use a skillet over medium-low heat and cover for a few minutes until warmed through and the cheese melts. Avoid microwaving if you want to preserve crispness; the microwave will make the crust chewy and limp.

Freezing assembled sandwiches is possible but not ideal because the spinach and mayo can change texture. If you must, freeze wrapped sandwiches in an airtight container and thaw overnight in the fridge before reheating in a skillet or a 350°F oven until warmed through.

Reader Q&A

Q: Can I use fresh spinach instead of frozen?

A: Yes. Use about 4 cups fresh spinach, sauté briefly to wilt, then squeeze out excess moisture in a towel. Fresh spinach has a milder texture and a brighter taste, but it needs the same attention to moisture.

Q: How can I make more than two sandwiches?

A: Double the recipe and bake two crusts or use long flatbreads and cut into pieces after baking. Work in batches when cooking chicken and pan-frying sandwiches so you don’t overcrowd the skillet.

Q: My crust cracked while pressing — what went wrong?

A: The crust may have been stretched too thin or over-handled. Press gently and evenly into the pan, and don’t overwork it. If it tears, patch it with a bit of excess dough and dock lightly so it bakes evenly.

Let’s Eat

Cut each sandwich in half to show off the layers: the glossy, garlicky mayo, the white ribbons of provolone, the green of the spinach, and the dark-sweet onions. Serve immediately while the exterior is crisp and the cheese is melty. A simple side salad or pickles complement the richness and make this a complete, satisfying meal.

Make one for yourself first to test the heat and press time on your stovetop; once you dial that in, this sandwich becomes one of the easiest ways to impress friends and family on short notice. Enjoy.

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