Grease a 12 cup muffin tin lightly with cooking spray.
Add bread cups to each tin, filling to top (bread will shrink down once wet ingredients are added). Set aside.
In a medium bowl, whisk together milk, heavy cream, eggs, sugar, vanilla, cinnamon, and nutmeg. Pour egg mixture over each tin. Lightly press down with a spoon to ensure that each piece of bread is saturated, if necessary.
Cover with plastic wrap and refrigerate for at least 3 hours or overnight.
When ready to bake, preheat oven to 375°F. Bake for 15-20 minutes or until tops are golden brown and middle is soft (but not gooey).
Let cool in pan for 10 minutes and then remove. Serve with maple syrup, if desired.