Preheat oven to 325°F (165°C). Line a 9 x 13-inch dish with foil, letting the foil extend over the edges for easy lifting.

Pulse Oreo cookies, cream included, in a food processor until they become fine crumbs.

Mix together crumbs and melted butter until evenly moistened. Press evenly into the bottom of the prepared pan to form the crust.

Bake crust for 11 minutes. Remove and cool.

Place a large sheet pan on the bottom oven rack and fill it half full of water for a water bath.

In a large bowl, beat cream cheese and granulated sugar until creamy and free of lumps.

Add sour cream and flour and beat until smooth.

Add eggs and beat just until mixed in; avoid overbeating.

Remove 1 cup of batter and set aside. Pour melted white chocolate and Creme de Menthe into the remaining batter and mix until evenly combined.

Pour the mint-white chocolate batter over the cooled crust.

Add the melted semisweet chocolate to the reserved cup of batter, mix, and drop dollops over the cheesecake batter. Swirl gently with a knife to create marbled ribbons.

Place the pan of cheesecake on the oven rack above the steaming water and bake for 50-55 minutes, or until the sides are set and the center is slightly wiggly. Remove and cool on a rack for an hour, then refrigerate until fully chilled.

Chill the mixing bowl and beaters in the freezer for 10 minutes.

Beat heavy cream and powdered sugar until stiff peaks form. Swirl or spread over the chilled cheesecake bars and finish with sprinkles if desired.

Lift the chilled slab from the pan using the foil overhang and slice with a warm, dry knife for clean edges.

Serve small squares on chilled plates, optionally garnished with a thin mint or a shard of white chocolate.