Prepare the Crust: In a mixing bowl, combine graham cracker crumbs, granulated sugar, cinnamon, and melted unsalted butter. Using a fork, mix until the crumbs are evenly moistened. Line a muffin tin with paper liners and press the crust mixture firmly into the bottom of each liner. Chill in the refrigerator for about 15 minutes to allow the crust to set.

Make Filling: In a large mixing bowl, beat the softened cream cheese, granulated sugar, vanilla extract, all-purpose flour, and egg using an electric mixer until smooth and creamy. Be cautious not to overmix.

Prep Apples: Peel, core, and dice the Golden Delicious apples into small pieces. Toss the diced apples with lemon juice, brown sugar, cinnamon, nutmeg, and cornstarch; set aside.

Combine Layers: Remove the crust from the refrigerator. Spoon the cheesecake filling into each lined cup, filling them about three-quarters full. Layer the apple mixture on top of the cheesecake filling.

Prepare Streusel: In a medium bowl, mix oats, flour, brown sugar, and melted butter until the topping is crumbly. Sprinkle this oat mixture over the apple layer in each mini cheesecake.

Bake: Preheat your oven to 325°F (160°C). Bake for 28-30 minutes until the edges are set, and the centers jiggle slightly.

Cool: Allow the cheesecakes to cool in the pan for 30 minutes at room temperature, then transfer to the refrigerator for at least an hour.

Serve: Drizzle with caramel sauce and add a dollop of whipped cream before serving.