Key Lime Fudge
This Key Lime Fudge takes the sunny, bright flavor of key limes and folds it into a creamy, melt-in-your-mouth square that belongs on every spring and summer dessert table. It’s not a traditional custard or a pie; it’s a quick, stovetop fudge that relies on evaporated milk, marshmallows and white chocolate to get that silky texture while lime zest and juice cut through with freshness. It’s simple, fast, and reliably festive.
I make this when I want something that feels special but doesn’t require hours of oven time or fancy equipment. The lime flavor is bold without being sour—thanks to the combination of grated zest and a measured splash of key lime juice—and the marshmallows help set the fudge without tempering chocolate. If you like bright, citrusy treats that are easy to portion and pack for parties, this is that recipe.
Below you’ll find ingredient notes, step‑by‑step instructions taken straight from the tested method, swaps if you need them, and practical storage and prep tips. Read through once, then follow the steps in order—this fudge sets quickly when the temperature drops, so timing and stirring matter.
Ingredient Notes
Focus on fresh citrus and good white chocolate. The grated lime zest delivers essential aromatic oils that give the fudge its key-lime character; fresh zest is worth the little extra work. The evaporated milk and sugar create the candy base, while the marshmallows and white chocolate chips melt into a smooth, stable mass that sets firm but tender.
Key lime juice is more tart and floral than regular lime. If you only have Persian limes, the recipe will still work, but use the juice carefully and taste as you go. Also, use full-size large marshmallows and quarter them for faster, even melting. Finally, line the pan with foil with an overhang so you can lift the entire slab out cleanly for neat cutting.
Ingredients
- One 5-ounce can 2% evaporated milk — forms the creamy candy base and controls texture.
- 1⅔ cups granulated white sugar — sweetens and helps the mixture reach the right set when boiled.
- ½ teaspoon salt — balances sweetness and brightens lime flavor.
- 12 large marshmallows, quartered — act as a stabilizer to help the fudge set without tempering chocolate.
- 2 cups white chocolate chips — melt into a smooth, sweet foundation that pairs with lime.
- ¼ cup grated lime zest (about 5 limes) — essential aromatic oils; don’t skip and avoid the bitter white pith.
- 2 tablespoons key lime juice (5 to 7 limes, juiced) — provides the signature tartness; measure after juicing for best balance.
Key Lime Fudge, Made Easy
- Line an 8″ x 8″ square pan with aluminum foil, pressing the foil into the corners and leaving a 1–2″ overhang on two opposite sides to lift the fudge out later.
- In a large heavy saucepan (or a double boiler), combine one 5-ounce can 2% evaporated milk, 1⅔ cups granulated sugar, and ½ teaspoon salt.
- Place the pan over medium heat and stir until the sugar dissolves. Bring the mixture to a boil, stirring constantly.
- Once boiling, reduce the heat to medium-low and maintain a gentle, steady boil. Continue to boil for 5 to 6 minutes, stirring constantly to prevent scorching.
- Remove the pan from the heat immediately.
- Add 12 large marshmallows (quartered), 2 cups white chocolate chips, ¼ cup grated lime zest, and 2 tablespoons key lime juice. Stir continuously until the marshmallows and chocolate are completely melted and the mixture is smooth.
- Scrape the fudge mixture into the prepared foil-lined pan and tilt or spread it so it covers the bottom evenly. Smooth the top with a spatula.
- Cool the fudge completely at room temperature (or chill until firm).
- Use the foil overhang to lift the set fudge from the pan and cut into 1-inch squares.
Why I Love This Recipe
It’s fast and forgiving. There’s no tempering, no candy thermometer, and very little hands-on time once the sugar reaches a boil. The texture is smooth and a little pillowy from the marshmallows; the white chocolate gives richness without the heaviness of cream or butter. The lime elements are layered—zest for aroma and juice for immediate tang—which makes each bite lively.
It’s also a portable dessert. Cut into small squares, the fudge travels well for potlucks and picnics because it doesn’t crumble like a cake or melt like soft ice cream. It’s a bright alternative to the usual chocolate fudge if you want something that stands out visually and on the palate.
Dairy-Free/Gluten-Free Swaps
Dairy-free substitutions can work, but choose swap components carefully:
- For a dairy-free approach, use dairy-free white chocolate chips and a suitable evaporated milk substitute (look for canned coconut evaporated milk or a concentrated coconut milk labeled for cooking). The result will skew coconut-forward.
- Use vegan marshmallows to keep the set and texture while avoiding gelatin.
- The recipe is naturally gluten-free if you use gluten-free white chocolate chips and check marshmallow labeling.
Tools & Equipment Needed
- 8″ x 8″ square pan — the recipe is tested for this size for proper thickness and set.
- Aluminum foil — for lining and the overhang to lift the fudge out cleanly.
- Large heavy saucepan or double boiler — prevents scorching during the sugar boil.
- Spatula and wooden spoon — spatula for spreading, wooden spoon for stirring.
- Microplane or fine grater — for zesting limes without getting pith.
- Citrus juicer — handy for extracting 5–7 key limes worth of juice efficiently.
Don’t Do This
- Don’t walk away during the boil. The sugar stage requires constant stirring to prevent scorching and to keep a steady, gentle boil.
- Don’t skip the foil overhang. Without it, removal and clean cuts are messy and difficult.
- Don’t substitute bottled lime juice for all the flavor. Bottled juice lacks the bright aromatic oils you get from fresh zest; use fresh zest regardless.
- Don’t try to speed cooling with extreme heat changes. Rapid chilling can cause sugar bloom or a grainy texture; let it cool to set calmly or chill until just firm.
Better-for-You Options
If you want to lighten this fudge slightly without changing structure too much, focus on portion control and ingredient choices rather than altering cooking chemistry. Use smaller squares, serve with fresh fruit, or make a shallow pan so pieces are thinner.
For lower added sugar per serving, cut the finished slab into smaller pieces. Using high-quality white chocolate with fewer additives can improve flavor so you perceive sweetness without needing larger portions.
If You’re Curious
Why do marshmallows help set fudge? Marshmallows contain gelatin, corn syrup and sugar, which together help stabilize and bind the mixture as it cools. They allow you to avoid a separate tempering step for chocolate while still achieving a firm, sliceable texture.
Why not use heavy cream? The evaporated milk and sugar boiled together create a candy base that’s firm when cooled. Heavy cream would make the mixture richer and softer and would change the cooking time and final texture.
Can you use regular lime instead of key lime? Yes, but key limes are more aromatic and floral. If you use regular limes, taste carefully and adjust the juice—start with less and add as needed.
Prep Ahead & Store
You can make Key Lime Fudge a day or two in advance. Store it in an airtight container with parchment between layers to prevent sticking. At room temperature it will remain sliceable for a couple of days in a cool kitchen; in warmer climates, refrigerate to keep it firm. If chilled, let pieces sit at room temperature for 10–15 minutes before serving so they soften slightly and the flavors open up.
For longer storage, wrap individual squares tightly and freeze for up to 2 months. Thaw in the refrigerator overnight, then bring to room temperature before serving to avoid condensation on the chocolate surface.
Quick Questions
- How long does this take to set? Allow it to cool completely at room temperature or chill until firm—typically a couple of hours at room temp or under an hour refrigerated.
- Do I need a candy thermometer? No. The recipe uses timing and constant stirring rather than a temperature target.
- Can I halve or double the recipe? Halving is possible but be careful with pan size—thickness will change. Doubling is easier if you use a larger pan and adjust cooling time.
- Why is the zest amount so high? ¼ cup grated lime zest equals aromatic oils that carry the key lime profile; without it the fudge tastes only of white chocolate.
Ready, Set, Cook
Gather your ingredients and line the pan first. The cooking stage moves quickly once the sugar boils. Stir steadily, work efficiently, and don’t be intimidated by the short cooking time—attention is the main ingredient here. When the slab is set, lift with the foil overhang and cut 1-inch squares for tidy servings.
This fudge makes a lovely gift: wrap small stacks in parchment and tie with a bright ribbon. Serve it on a dessert board with fresh berries for a balance of sweet and tart. Enjoy the bright lift of lime in a treat that’s easier than it looks.
Key Lime Fudge
Ingredients
Ingredients
- One5-ounce can2% evaporated milk
- 1 2/3 cupsgranulated white sugar
- 1/2 teaspoonsalt
- 12 largemarshmallows quartered
- 2 cupswhite chocolate chips
- 1/4 cupgrated lime zest about 5 limes
- 2 tablespoonskey lime juice 5 to 7 limes, juiced
Instructions
Instructions
- Line an 8" x 8" square pan with aluminum foil, pressing the foil into the corners and leaving a 1–2" overhang on two opposite sides to lift the fudge out later.
- In a large heavy saucepan (or a double boiler), combine one 5-ounce can 2% evaporated milk, 1⅔ cups granulated sugar, and ½ teaspoon salt.
- Place the pan over medium heat and stir until the sugar dissolves. Bring the mixture to a boil, stirring constantly.
- Once boiling, reduce the heat to medium-low and maintain a gentle, steady boil. Continue to boil for 5 to 6 minutes, stirring constantly to prevent scorching.
- Remove the pan from the heat immediately.
- Add 12 large marshmallows (quartered), 2 cups white chocolate chips, ¼ cup grated lime zest, and 2 tablespoons key lime juice. Stir continuously until the marshmallows and chocolate are completely melted and the mixture is smooth.
- Scrape the fudge mixture into the prepared foil-lined pan and tilt or spread it so it covers the bottom evenly. Smooth the top with a spatula.
- Cool the fudge completely at room temperature (or chill until firm).
- Use the foil overhang to lift the set fudge from the pan and cut into 1-inch squares.
Equipment
- 8 x 8-inch square pan
- Aluminum Foil
- large heavy saucepan
- double boiler (optional)
- Spatula
Notes
*This recipe can be made with regular limes too.
