1. Preheat oven to 325°F (163°C). Pulse 24 Oreos in a food processor until finely crushed, then mix with melted butter. Press firmly into a 9-inch springform pan. Bake for 10 minutes and set aside.

2. In a bowl, whisk flour, cocoa powder, baking soda, and salt. In a separate bowl, mix sugar, oil, egg, buttermilk, vinegar, vanilla, and purple gel food coloring. Combine wet and dry ingredients until smooth.

3. Pour velvet batter over the baked crust. Bake for 18–20 minutes or until a toothpick comes out clean. Let cool in the pan.

4. Beat cream cheese with sugar until smooth. Mix in sour cream and vanilla. Add eggs one at a time until just combined. Fold in crushed Oreos if using.

5. Pour cheesecake batter over cooled velvet cake layer. Tap to remove air bubbles. Wrap pan in foil and place in a water bath.

6. Bake for 50–60 minutes or until center is slightly jiggly. Turn off oven and cool cheesecake inside with door cracked open for 1 hour.

7. Cool to room temp, then refrigerate for at least 6 hours or overnight.

8. Decorate with whipped cream, Oreos, and optional chocolate shavings or ganache. Slice with a warm knife and serve.