Cut 5 slices of bread into cubes (about 1-inch square) and place in a large mixing bowl.
Add dry ingredients (1/2 cup garbanzo flour, 2 tbsp sugar, 1/2 tsp cinnamon, 1/4 tsp salt, and 1/4 tsp nutmeg) to a small mixing bowl and give them a stir.
Add 3/4 cup plant milk, 1/3 cup melted vegan butter, and 1 tsp vanilla, and stir with a whisk until you have a smooth batter. (Don't taste the batter! It's awful before it's cooked).
Pour the mixture over the bread cubes and fold them over with a rubber spatula until they are well coated and have soaked up all of the batter.
Put 2 tablespoons of any neutral-flavored oil in the bottom of an 8" x 8" casserole dish and then pour in the saturated bread cubes and top with berries.
Make the crumble topping
Add softened butter, flour, oats, brown sugar, cinnamon, nutmeg, salt, and baking soda to a medium-sized mixing bowl. Mix with the back of a fork or a pastry cutter until crumbly.
Sprinkle the top of the casserole with the crumble topping.
Bake immediately or cover and place in the fridge for up to 48 hours before baking.
Bake and serve
Preheat your oven to 375° F (190° C), then once it reaches temperature, place the casserole in the oven uncovered for 40-45 minutes until the top is slightly brown and crispy.
Scoop out with a spatula and serve with a drizzle of maple syrup.
Notes
Use a good quality bread that is a day or two old so it's a little dry so it soaks up the batter. You don't want wet spongy bread.
If your bread seems too moist, place the cubes on a cookie tray in a 200° F oven for about 10 minutes until it dries out.
Don't skimp on the butter or oil in this recipe or it will be too dry and stick to the bottom of your baking dish.
Don't taste the chickpea batter! Raw chickpea batter tastes terrible before it's cooked. It's delicious once it's cooked, but be sure that you don't have any wet raw batter in your casserole.
To serve a large group of people, double the recipe and bake in a 9" X 11" baking dish. It may need to cook for about 5 extra minutes.