Preparation
To make the crust, preheat oven to 350°F. Lightly grease a 9" springform pan with nonstick baking spray or butter.
Using a food processor or chopper, chop the cookies into crumbs. Alternatively, you can place the cookies in a resealable plastic bag and crush them into crumbs.
Mix together the cookie crumbs and melted butter in a mixing bowl and press this mixture into the bottom of the greased springform pan. Use a flat-bottomed measuring cup or spatula to smooth and compress the cookie crumbs. Bake for 8–10 minutes, then cool completely.
To make the filling, increase oven temperature to 425°F. Heat a kettle of water (8–12 cups) to boiling.
Using a stand mixer fitted with a flex edge beater, beat the cream cheese and sugar until light and fluffy. Mix in the cornstarch, then the vanilla. Add the 3 eggs and 1 egg yolk, one at a time. Mix in the peanut butter, then the sour cream. Stop mixing to scrape the bottom of bowl, then mix a little longer to ensure everything is thoroughly combined. It should have a smooth, satiny texture.
Pour the filling into the cooled crust in the springform pan. Gently smooth the top and tap the pan on the counter a couple of times to eliminate any large pockets of air.
Next, lay 2 (17"-long) sheets of heavy duty (18"-width) aluminum foil in a crisscross shape on the counter.
Place the filled springform pan in the center of the foil sheets and gently fold the foil up and around pan. It doesn't have to be tightly pressed around the pan, just make sure not to create any holes in the foil. Place the foil-wrapped pan in a roasting pan, then put the roasting pan, with the cheesecake inside, into the preheated oven. Gently pour the heated water from the kettle into the roasting pan, taking care not to splash water onto the cheesecake. The water should come about halfway up the springform pan.
Bake at 425°F for 10 minutes. Reduce the oven temperature to 200°F, keeping the oven door closed. Bake for another 45 minutes.
Turn off the oven and allow the cheesecake to cool in the oven for 3 hours, leaving the door slightly ajar. (You can tuck the end of a wooden or silicone spoon into the top corner of the oven door for this.)
Remove the cheesecake from the oven, being careful again not to splash any water. Remove the springform pan from the water bath and unwrap the foil. Run a thin knife or spatula around the edge of the cheesecake to release it from the pan. Place the cheesecake in the refrigerator, uncovered, until slightly chilled (to help prevent condensation), then cover it with plastic wrap and refrigerate for at least 4 hours or overnight.
You can refrigerate the cheesecake, wrapped tightly in foil, for up to 4 days or freeze it for up to 3 months. If frozen, thaw it out overnight in the refrigerator before proceeding.
When ready to serve (after refrigerating), run a thin knife or spatula around the edge of the cheesecake again to make sure it's released from the pan. Remove the outside ring of the springform pan. If there's moisture on top of the cheesecake, you can gently lay a paper towel on top to absorb it.
To make the ganache, place the chocolate chips in a medium-size, heat-proof bowl. Then, heat the heavy cream to simmering in a saucepan or in the microwave. Pour the hot cream over the chocolate chips and allow to sit for a minute or two. Stir until the chocolate chips melt into the cream and the mixture becomes smooth. If the mixture cools before all of the chocolate chips melt, you can microwave it for about 20 seconds.
Pour the chocolate ganache topping over the cheesecake. Use an offset spatula or the back of a spoon to spread the topping over the surface, allowing some to drip over the edge. Chill for 20 minutes to set the ganache. If desired, garnish with the whipped cream and mini peanut butter cups. Remove from the refrigerator 20–30 minutes before serving. To achieve a clean cut, dip the knife in warm water before cutting each slice, wiping the knife clean in between.
