– cooking spray – 6 large egg – 1 cup milk – 1/2 cup heavy cream – 2 tablespoons brown sugar – 2 teaspoons vanilla extract – 2 teaspoons ground cinnamon – 1/4 teaspoon salt – 8 large croissants (about 1 1/4 pounds), halved horizontally – confectioner's sugar, fresh berries, or maple syrup for serving