1-First Step: Prepare the bread base Cut 8 cups of day-old French or brioche bread into 1-inch cubes. Spread them evenly in the greased 9×13-inch dish. Press down gently to fit snugly. This sturdy bread absorbs the custard best, avoiding sogginess. For gluten-free, use a certified loaf here.

2-Second Step: Make the egg custard mixture Whisk 8 large eggs, 2 cups milk, 1/2 cup heavy cream, 1/2 cup sugar, 1/4 cup maple syrup, 2 tsp vanilla extract, and 1 tsp cinnamon in a large bowl. Beat until smooth, about 1-2 minutes. This blend creates the signature custardy texture of french toast casserole. Taste and adjust cinnamon for vegan versions with plant milks.

3-Third Step: Assemble with blueberries Scatter 2 cups fresh or frozen blueberries over the bread cubes. No need to thaw frozen ones; they release juices during baking. Pour the custard slowly over everything. Gently toss and press down so bread soaks fully. Cover with plastic wrap or foil. For low-calorie, drizzle half the custard first to control richness.

4-Fourth Step: Overnight soak or quick prep Refrigerate for 8-24 hours for maximum flavor absorption in this overnight blueberry french toast casserole. Or bake right away if rushed. The soak turns simple ingredients into a moist, flavorful bake. Let it sit at room temp for 20-30 minutes before baking if chilled.

5-Fifth Step: Add streusel and bake Mix 1/2 cup flour, 1/2 cup brown sugar, 1 tsp cinnamon, and 1/2 cup cold cubed butter with a fork or fingers until crumbly. Sprinkle over the top. Bake uncovered at 350°F for 45-50 minutes. Look for puffed, golden edges and set center no jiggle. Vegan streusel works with coconut oil. Cool 10 minutes before serving.

6-Final Step: Finishing touches and serving Dust with powdered sugar and drizzle maple syrup. Slice into squares. Pair with coffee or yogurt for busy parents. Leftovers reheat beautifully. This easy blueberry french toast casserole wows every time. Total time: about 1 hour active plus chill.