Lightly spray a 9x13 inch baking dish with cooking spray or brush with butter. Put bread cubes in baking dish and top with raspberries and shredded coconut.
In a medium bow, whisk together brown sugar, eggs, coconut milk, and vanilla extract until smooth. Pour mixture over bread. Cover baking dish in plastic wrap and place in fridge for at least 4 hours, but preferable overnight.
In the morning, pre-heat oven to 350 degrees. Remove plastic wrap from baking dish and sprinkle crumb topping over casserole. Place in oven for 45-55 minutes, until casserole is cooked through and no longer jiggly. If the top is browning too much, but you want inside to cook longer, cover top with tinfoil.
Remove from oven and let rest for 5 minutes before topping with additional coconut (if desired) and serving.