Spray 9 x 13-inch baking pan with cooking spray. Tear bread into chunks and place in the pan.
Mix together eggs, milk, sugar, and vanilla. Pour evenly over bread. Cover tightly and store in the fridge several hours or overnight.
In a separate bowl, mix flour, brown sugar, cinnamon, and salt. Add butter pieces and incorporate into the dry mixture with a large fork until it resembles pebbles. Store crumb topping until you are ready to bake the french toast.
When you're ready to bake the french toast, preheat oven to 350 degrees. Remove casserole from fridge, add fresh berries on top, and sprinkle crumb mixture over the top. Bake for 45 minutes to 1 hour, depending on your desired texture.
Serve warm.
Recipe by 2 Sisters 2 Cities at https://www.2sisters2cities.com/2012/06/baked-french-toast/