Preheat oven to 375°F and grease a 9x13-inch baking dish.

Layer cubed croissants in the baking dish and set aside.

In a skillet, melt butter, then add brown sugar, cinnamon, and nutmeg. Stir until smooth.

Add diced apples and cook for 5 minutes, stirring often. Mix cornstarch and water, then stir into apples. Add lemon juice and remove from heat.

In a bowl, whisk together heavy cream, applesauce, eggs, vanilla, and cinnamon.

Spoon apple mixture over croissants, then pour custard mixture evenly over top.

Bake for 35–40 minutes or until golden and set.

Mix powdered sugar, cream, and vanilla to make icing. Drizzle over casserole after it cools for 5 minutes.