Preheat oven to 350°F. Pulse cookies into fine crumbs, mix with 1/4 cup sugar and melted butter, and press into a 9-inch springform pan. Bake 10 minutes, then cool and reduce oven to 325°F.

Beat cream cheese until smooth, add 1 cup sugar, cocoa, buttermilk, vanilla, vinegar, salt, and mix on low. Reserve 1 cup plain batter.

Add red gel coloring and cornstarch to the remaining batter, then beat in eggs one at a time on low. Drop plain batter over the red, pour into crust, and swirl with a knife.

Wrap pan in foil, set in a roasting pan, and add hot water halfway up. Bake at 325°F for 60–70 minutes until edges are set and center jiggles slightly.

Turn off oven, crack door, and let cheesecake cool inside for 1 hour. Remove from water bath, cool to room temperature, then cover and refrigerate for at least 6 hours, ideally overnight.

Remove pan sides, top with whipped cream, and slice with a hot knife.