Preheat oven to 425°F and butter a 9 by 13-inch baking dish.
Cut or tear your bread loaf into cubes.
1 loaf white bread
In a saucepan over medium heat, melt butter. Add brown sugar and mix well, until the sugar dissolves completely and the mixture is smooth and beginning to thicken.
1 cup brown sugar, ½ cup butter
Pour the mixture into the bottom of your greased baking dish. Smooth out evenly across the bottom of the dish.
Add cubed bread to the baking dish.
In a bowl, whisk together eggs, milk, vanilla, cinnamon, and brown sugar. Once whisked well, pour egg mixture over the cubed bread. Make sure all pieces of bread have been soaked with the mixture.
8 large eggs, 3 cups milk, 3 teaspoons vanilla extract, 3 teaspoons cinnamon, 1 Tablespoon brown sugar
Bake 25-30 minutes, or until the top is golden brown and fluffy. Remove from the oven and top with powdered sugar and fresh fruit if desired. Enjoy!
Fresh fruit - optional, Powdered sugar
Video
Notes
If your casserole is browning too quickly, cover it with foil for part of the cooking time.
I recommend using brioche or challah bread for this recipe, or a nice thick sourdough. Don't bother with regular sliced white bread; it's so thin and airy, it will just turn to mush.
1-2 days old bread works best for French toast as it holds up better to the liquid. If you're using a fresh loaf, just leave the loaf out, unwrapped, for 1-2 hours. You can even speed up the process by tearing it into cubes and leaving them out for 30 minutes.
If you want to avoid dairy milk, you can use almond, oat, or coconut milk instead.