Preheat the oven to 350°F. Generously coat a 9x13 baking dish with cooking spray (collagen has a tendency to stick when baking, make sure you’re dousing the pan with spray oil!)
Use a serrated edge knife to slice each piece of bread into 9 cubes (3 rows & 3 columns).
Then, in a large mixing bowl whisk together: egg, milk, cottage cheese, vanilla extract, cinnamon & maple syrup and collagen. Use an immersion blender to blend the cottage cheese until no more clumps remain.
Add the cubed bread pieces into the greased casserole dish, then pour the egg mixture over top. Top with fresh berries. Stir the mixture together so the bread is covered in mixture and berries are evenly distributed.
Bake for 40-45 minutes or until center has set, fruit has wilted and bread is toasted (if you notice the top of the bread getting too crispy, cover the pan with foil for the last few minutes of bake time to prevent burning).
While the french toast casserole is baking, use a hand mixer to beat together frosting ingredients. Add milk until a drizzle consistency is reached.
Then, drizzle it over the baked casserole and let it soak into the bread. I recommend topping with more berries and maple syrup.