Our favorite part of these creamy, sweet-and-salty bars is the crust: Melted chocolate and just a little bit of butter make it crunchy without baking. Plus, you can skip the full fat sour cream in the cheesecake layer. Buttermilk adds just the right tang.
Special equipment: An offset spatula
Line an 8-inch square pan with foil so it overhangs on two sides and lightly spray the foil with nonstick cooking spray. Put the chocolate and butter in a medium microwave-safe bowl and microwave, stirring every 30 seconds, until the chocolate is melted and smooth, about 1 minute.
Put the graham crackers in a food processor and process until finely ground. Add the melted chocolate mixture and process until the mixture is the texture of very wet sand. Press the crust into the bottom of the prepared pan, cover and refrigerate while preparing the cheesecake layer.
Clean out the food processor bowl. Sprinkle the gelatin over 2 tablespoons water in a small microwave-safe bowl and set aside to soften, about 5 minutes. Microwave the dissolved gelatin, stirring every 10 seconds, until melted.
Combine the cream cheese, buttermilk, peanut butter, brown sugar, vanilla, salt and melted gelatin in the food processor and process until smooth and the sugar has dissolved. Rub a little of the mixture between your fingers, if it is still gritty then continue to process.
Pour the cream cheese mixture over the crust and spread evenly with an offset spatula. Sprinkle the top with the peanuts. Wrap the pan loosely with plastic wrap and refrigerate until the cheesecake layer is set, about 2 hours. The bars can be assembled and refrigerated overnight. Cut into 12 bars.