In a small bowl, combine pretzels and butter. Press onto the bottom and 1 in. up the sides of a greased 10-in. springform pan. Place pan on a baking sheet. Bake at 350° for 5 minutes. Cool on a wire rack., In a large bowl, beat cream cheese and sugar until smooth. Add peanut butter and vanilla; mix well. Add eggs; beat on low just until combined. Stir in chips. Pour over the crust. Return pan to baking sheet., Bake at 350° for 50-55 minutes or until center is almost set. Remove from the oven; let stand for 15 minutes (leave oven on)., For topping, in a small bowl, combine the sour cream, peanut butter and sugar; spread over filling. Sprinkle with nuts. Bake 5 minutes longer., Cool on a wire rack for 10 minutes. Carefully run a knife around the edge of the pan to loosen; cool 1 hour longer. Refrigerate overnight. Remove sides of pan. Refrigerate leftovers.