If your bread is not already sliced, cut it into about 3/4" thick slices (about 8–10 slices per 1 lb). Arrange slices on a wire rack to dry for 1–2 hours if time permits. Preheat the oven to 275°F.
Warm the 1 Tbsp honey until pourable. In a medium bowl, whisk together 6 large eggs, 2 large egg yolks, 1 cup whole milk, 1/4 tsp salt, 2 tsp vanilla extract, 1 tsp ground cinnamon, and the warmed 1 Tbsp honey until well blended and the honey is dissolved.
Pour the egg mixture into a shallow casserole dish or baking dish large enough to fit up to 4 slices at a time (or as many as will fit in your skillet).
Place a skillet over medium-low heat. Add 2 Tbsp unsalted butter and melt, coating the pan.
Dip 4 bread slices at a time into the egg mixture, soaking each slice about 30–40 seconds per side (adjust time for thickness). Lift each slice and let excess custard drip back into the dish.
Place the soaked slices into the hot skillet without overcrowding and cook 3–4 minutes per side, until golden brown.
Transfer the cooked slices to a baking sheet and place the sheet in the oven at 275°F to keep warm.
Add the remaining 1 Tbsp unsalted butter to the skillet as needed, melt, and repeat steps 5–7 with the remaining bread slices.
After all slices are sautéed and on the baking sheet, keep them in the oven for another 10–15 minutes to ensure the custard center is fully set.
Remove from the oven and serve warm.