Prepare the Crust:

1. Make the Crust: In a medium bowl, mix together the graham cracker crumbs, sugar, and melted butter until the crumbs are fully coated.
2. Press into Pan: Spoon about 1-2 tablespoons of the crumb mixture into the bottom of each mini cheesecake cup or muffin tin. Use the back of a spoon or your fingers to press the crumbs down firmly to form the crust.

Make the Apple Topping:

3. Cook the Apples: In a small pan, melt the butter over medium heat. Add the diced apples, brown sugar, and cinnamon. Cook, stirring occasionally, until the apples are softened, about 5-7 minutes.
4. Add Oats and Flour: Stir in the oats and flour, and cook for another 2-3 minutes until the mixture thickens and becomes crumbly. Remove from heat and set aside to cool slightly.

Make the Cheesecake Filling:

5. Prepare the Cheesecake Filling: In a large mixing bowl, beat the softened cream cheese with the sugar until smooth. Add in the vanilla extract and eggs, one at a time, beating well after each addition. Mix in the sour cream until the filling is smooth and creamy.
6. Fill the Cups: Spoon the cheesecake filling over the prepared crust in each mini cheesecake cup, filling them almost to the top.

Assemble and Bake:

7. Top with Apples: Spoon the cooked apple mixture on top of the cheesecake filling, dividing it evenly among the mini cheesecakes.
8. Bake: Preheat your oven to 325°F (163°C). Bake the mini cheesecakes for 18-20 minutes or until the edges are set, and the centers are slightly jiggly. The tops should be golden brown from the apple topping.
9. Cool and Chill: Allow the cheesecakes to cool to room temperature before transferring them to the fridge to chill for at least 30 minutes before serving.