Preheat your oven to 325°F (160°C) and line a muffin tin with paper liners.

In a medium bowl, combine the graham cracker crumbs, melted butter, and brown sugar. Mix well until the crumbs are evenly coated.

Press about 2 tablespoons of the crumb mixture into the bottom of each muffin liner to form the crust. Bake for 10 minutes, until lightly golden, then remove and let cool.

In another bowl, toss the diced apples with lemon juice, cinnamon, brown sugar, and cornstarch. Mix until well coated, then set aside.

In a large mixing bowl, beat the softened cream cheese until smooth. Add sour cream, sugar, eggs, and vanilla extract. Mix on medium speed until everything is well blended and creamy.

Pour the cream cheese mixture over the cooled crusts, filling each liner about halfway. Spoon the prepared apple filling on top, distributing evenly.

In a separate bowl, mix oats, flour, brown sugar, melted butter, and cinnamon to create the crumb topping. Sprinkle it generously over the apple filling.

Bake for an additional 15-20 minutes or until the centers are set and the tops are slightly golden.

Once baked, allow the mini cheesecakes to cool completely in the muffin tin before refrigerating for at least 2 hours.

Enjoy these beauties chilled or at room temperature!