In a large bowl, mix together the white granulated sugar, brown sugar, vanilla extract, cinnamon, nutmeg, eggs, milk, and heavy cream. Whisk until fully smooth and incorporated.
Cut the french bread into 1-inch cubed pieces. Place in the milk mixture bowl, fully submerge until all the pieces have absorbed the mixture.
Spray a 12-cup muffin tin really well with coconut oil cooking spray. Begin to scoop the french toast mixture into each cup. Once all the mixture is in the cups, bake at 350 degrees Fahrenheit for 30 minutes.
Carefully remove the muffins from the oven. Let them sit for 5 minutes. Carefully, scoop each muffin out. Top with maple syrup and serve immediately. Dust each muffin with powder sugar if desired before serving.
Recipe Notes: You can add a sprinkle of turbinado sugar on top of each muffin before baking to add an additional layer of sweetness and crunch.