Chocolate-Peanut Butter Cheesecake

Butter the inside of a 9" springform pan. Set rack in middle of oven and preheat to 350°. In a food processor or blender, grind chocolate graham crackers into fine crumbs. Add sugar and salt and pulse to combine. Transfer to a medium bowl, add butter, and use fork or fingers to blend mixture until crumbs are evenly moist. Press into bottom and about a third of the way up the sides of springform pan. Freeze 10 minutes. Place pan on baking sheet and bake crust for 10 minutes. Set on rack to cool and reduce oven temperature to 325°. Meanwhile, bring a medium saucepan or tea kettle full of water to a boil.  In a large bowl using a hand mixer or in the bowl of a stand mixer using the whisk attachment, beat cream cheese on medium, scraping down the bowl as necessary, until completely smooth, 3 to 4 minutes. Add sugar and salt and beat, scraping down bowl as necessary, until smooth and fluffy, 3 to 4 minutes. Add vanilla and beat for 30 seconds.  Add eggs, 1 at a time, beating for 1 minute after each addition and occasionally scraping bottom and sides of bowl. Add peanut butter, heavy cream, and sour cream and beat on low until completely smooth and streak-free, about 1 minute. Pour cheesecake batter into cooled crust and smooth top.  Wrap bottom of springform pan with a double layer of aluminum foil and place in a large roasting pan. Pour in enough boiling water to come up halfway up sides of springform pan.  Bake cheesecake until top is just starting to brown and crack, about 1 hour and 30 minutes. Turn off oven, prop door open with wooden spoon, and let cheesecake slowly cool in water bath for 1 hour. Remove roasting pan from oven, then carefully lift springform pan out of water and remove foil. Set cheesecake on rack and let come to room temperature. Once completely cool, loosely cover cheesecake with plastic wrap and refrigerate, 4 hours, or preferably overnight. When ready to serve, carefully remove sides of springform pan. Place chocolate in a clean, dry medium bowl. In a small saucepan over medium heat, warm cream until just barely simmering. Pour warm cream over chocolate and let sit 10 minutes, then add salt and stir until smooth.  Pour ganache over cheesecake, spreading it evenly and allowing some to drip down sides of cake. Sprinkle with chopped Reese's.