Prepare the crust:
Preheat oven to 325°F (163°C). Line a 12-count muffin pan with paper liners. In a small bowl, combine graham cracker crumbs, sugar, and melted butter. Divide the mixture evenly between the liners (about 1 tablespoon per cup). Press firmly into the bottom. Bake for 5 minutes, then let cool.

Make the cheesecake filling:
In a large bowl, beat softened cream cheese until smooth. Add sugar and mix until combined. Beat in eggs one at a time. Add vanilla extract and sour cream, mixing on low speed until smooth.

Fill and bake:
Spoon the cheesecake batter evenly over the cooled crusts, filling each muffin cup about three-quarters full. Bake for 18–20 minutes, or until the centers are set and no longer jiggle. Let cool for 30 minutes, then refrigerate for at least 2 hours.

Prepare the apple pie topping:
In a medium skillet, melt butter over medium heat. Add diced apples, brown sugar, cinnamon, and nutmeg. Cook for 5–7 minutes, stirring until apples soften. Stir in the cornstarch mixed with water and cook for another minute until thickened. Remove from heat and cool completely.

Assemble:
Once cheesecakes are chilled and firm, spoon about 1 tablespoon of apple topping onto each.

Serve and enjoy:
Garnish with whipped cream, caramel drizzle, or crushed graham crackers if desired. Chill again for 30 minutes before serving.