Brioche French toast casserole is a delicious and decadent make-ahead breakfast that's perfect for holiday mornings, lazy weekends, and special occasions.
Use butter or cooking spray to grease a 9" x 13" casserole dish.
Cut the bread into 1-inch cubes and spread evenly over the bottom of the pan.
In a large bowl, combine the eggs, milk, sugar and vanilla extract.
Pour the egg mixture over the bread cubes.
Cover the pan with aluminum foil and refrigerate 2 hours or overnight.
In another bowl, combine the flour, sugar, cinnamon, salt, and nutmeg.
Cut in the cold butter with a pastry cutter until the mixture resembles coarse crumbs.
Put the topping mixture in an airtight container or zip lock bag in the fridge.
Preheat oven to 350°
Sprinkle blueberries over the top of the bread.
Sprinkle topping evenly over the top of the casserole. Replace the foil cover.
Bake covered for 30 minutes, then remove the foil and bake another 30 minutes, until the top is golden brown.
Allow to cool for 10 minutes before serving with maple syrup.
Notes
Bread slices: Stale bread works really well for this overnight brioche French toast casserole. If you don't already have stale bread, You can spread the brioche slices on a baking sheet and dry the bread in a low oven (300°) for 20-30 minutes. Bread should be sliced fairly thick and cut into 1" cubes. If the brioche is cut into very small pieces you can end up with a soggy French toast bake.
Sugar: If you prefer less of a sweet flavor, you can easily reduce or even omit the brown sugar in the French toast itself. However, you do need the sugar for the streusel topping.
Add ins: I do love this blueberry French toast casserole, but this is an easy recipe to customize. I've made overnight French toast using other berries, like strawberries, blackberries, or raspberries. Apple or pear slices are lovely for fall. Try a tropical twist and stir in mango chunks, pineapple chunks (or both) and replace the cinnamon with shredded coconut. You can even go all-out decadent and add chocolate chips, topping with whipped cream. I sometimes like to add finely chopped pecans or flaked almonds to the topping, too.
Gluten-free: Use gluten-free bread (brioche if you can find it) and gluten-free flour for the cinnamon streusel.
Dairy-free: Use non dairy milk like almond milk, and use coconut oil for the topping.
Individual servings: You can divide the recipe into ramekins and place them on a baking sheet to bake for individual servings. Baking time may be reduced.
What to serve with: Baked French toast is perfect served with maple syrup for drizzling and sides of bacon or breakfast sausage, and fresh fruit.
Storage: Store leftover brioche French toast casserole in an airtight container in the fridge for up to three days. To reheat, microwave single servings briefly (20-30 seconds).
Freezing: Unbaked, you can freeze the casserole in the baking dish, tightly wrapped in foil and then plastic wrap. Defrost overnight in the fridge, then bake as instructed. I don't recommend freezing this recipe after baking because the texture will change once it's thawed and reheated.