Prepare the crust:

1. Preheat your oven to 350°F (175°C).
2. Grease a 9-inch springform pan and line the bottom with parchment paper to prevent sticking.
3. In a medium bowl, mix together 2 cups (200 g) of graham cracker crumbs, 1/4 cup (50 g) of granulated sugar, and 1/2 cup (115 g) of melted butter until well combined.
4. Press the mixture firmly into the bottom of the prepared pan. Bake for 8-10 minutes, then set aside to cool.

Make the cheesecake filling:

1. In a large mixing bowl, beat 3 packages (24 oz) of softened cream cheese and 1 cup (200 g) of granulated sugar with an electric mixer until smooth and creamy, about 3-5 minutes.
2. Add in the eggs, one at a time, mixing well after each addition.
3. Mix in 1/2 cup (120 ml) of sour cream and 1 teaspoon of vanilla extract until fully incorporated.
4. Pour the cheesecake filling over the cooled crust and spread evenly.

Prepare the apple layer:

1. In a separate bowl, toss 3 diced apples with 1/4 cup (50 g) of sugar, 1 teaspoon of cinnamon, and optional nutmeg.
2. Spread the apples evenly over the cheesecake filling.

Make the crisp topping:

1. In another medium bowl, combine 1/2 cup (60 g) of flour, 1/2 cup (40 g) of oats, 1/3 cup (65 g) of brown sugar, and 1/2 teaspoon of cinnamon.
2. Add in 1/4 cup (55 g) of cold, cubed butter and use a pastry cutter or your fingers to mix until crumbly.
3. Sprinkle the topping evenly over the apples.

Bake:

1. Place the cheesecake in the oven and bake for 55-65 minutes, or until the edges are set and the center is slightly jiggly.
2. Remove from the oven and let it cool to room temperature, about 1-2 hours.

Chill:

1. Cover the cheesecake and refrigerate for at least 4 hours, preferably overnight, to fully set.

Serve:

1. Remove the cheesecake from the springform pan and slice it into pieces.
2. Serve as-is or with a drizzle of caramel sauce for extra indulgence.