Very Vanilla Slow-Cooker Cheesecake

Grease a 6-in. springform pan; place on a double thickness of heavy-duty foil (about 12 in. square). Wrap foil securely around pan., Pour 1 in. water into a 6-qt. slow cooker. Layer two 24-in. pieces of foil. Starting with a long side, roll up foil to make a 1-in.-wide strip; shape into a circle. Place in bottom of slow cooker to make a rack., In a small bowl, mix cracker crumbs, 1 tablespoon sugar and cinnamon; stir in butter. Press onto bottom and about 1 in. up sides of prepared pan., In a large bowl, beat cream cheese and remaining sugar until smooth. Beat in sour cream and vanilla. Add eggs; beat on low speed just until combined. Pour into crust., Place springform pan on foil circle without touching slow cooker sides. Cover slow cooker with a double layer of white paper towels; place lid securely over towels. Cook, covered, on high 2 hours., Do not remove lid; turn off slow cooker and let cheesecake stand, covered, in slow cooker 1 hour., Remove springform pan from slow cooker; remove foil around pan. Cool cheesecake on a wire rack 1 hour longer. Loosen sides from pan with a knife. Refrigerate overnight, covering when completely cooled., For topping, in a microwave, melt chocolate and shortening; stir until smooth. Cool slightly. Remove rim from springform pan. Pour chocolate mixture over cheesecake; sprinkle with miniature peanut butter cups or almonds.