Preheat your air fryer to 325°F (163°C).

In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, whisk together the buttermilk, vegetable oil, egg, and vanilla extract.

Gradually add the wet ingredients to the dry ingredients, mixing until well combined.

Stir in the boiling water until the batter is smooth. It will be thin, but that's okay.

Pour the chocolate cake batter into a greased and lined 7-inch springform pan.

Place the pan in the preheated air fryer basket and cook for about 20-25 minutes or until a toothpick inserted into the center comes out clean.

Remove the cake from the air fryer and let it cool completely.

In a mixing bowl, beat the softened cream cheese and peanut butter until smooth and creamy.

Add the sugar and beat until well combined.

Add the eggs, one at a time, mixing well after each addition.

Stir in the sour cream and vanilla extract until the cheesecake batter is smooth.

Pour the peanut butter cheesecake batter over the cooled chocolate cake layer in the springform pan.

Return the pan to the air fryer and cook at 325°F (163°C) for another 15-20 minutes or until the edges are set, and the center is slightly jiggly.

Remove the cheesecake from the air fryer and let it cool to room temperature. Then refrigerate it for at least 4 hours or overnight.

In a microwave-safe bowl, combine the chocolate chips and heavy cream.

Microwave in 20-second intervals, stirring between intervals until the mixture is smooth.

Carefully remove the cheesecake from the springform pan.

Pour the chocolate ganache over the top of the cheesecake, allowing it to drip down the sides.

Sprinkle chopped Reese's Peanut Butter Cups on top.

Slice, serve, and garnish with whipped cream.