1. Crust: Preheat oven to 350 degrees. In a food processor, pulse wafers until finely ground. In a bowl, combine wafer crumbs, butter, brown sugar, and salt. Press mixture firmly into bottom and up sides of a 9-inch pie plate. Refrigerate until firm, about 15 minutes. Bake until set, 8 to 10 minutes. Let cool completely on a wire rack.

2. Filling: With an electric mixer on medium speed, beat cream cheese, confectioners' sugar, and salt until fluffy. Beat in peanut butter and vanilla.

3. In a chilled bowl, beat cream until soft peaks form. Whisk one-third of whipped cream into peanut butter mixture, then gently fold in remaining whipped cream. Spoon filling into cooled crust. Freeze, uncovered, 4 hours (or up to 1 day, covered with plastic wrap).

4. Garnish: Melt chocolate in heatproof bowl set over (not in) a pan of simmering water. (Alternatively, you can melt it in the microwave.) Transfer melted chocolate to a resealable plastic bag. Snip tip from one corner of bag to make a very small opening. Holding bag about 5 inches above pie, drizzle melted chocolate over top. In a small saucepan over low heat (or in the microwave), melt peanut butter. Place in a resealable plastic bag; snip corner, and drizzle in same manner as melted chocolate. Let pie stand 10 minutes before slicing.