Preheat oven to 350℉. In a food processor pulse together Nilla wafers, peanuts and sugar until you have a course uniform crumb. Drizzle in melted butter and pulse a few times to combine. Using 8, 4" mini tart pans with removable bottoms add 1/4 cup of crumb mixture to tart pan and evenly spread over the bottom and up the sides, pressing lightly to compact. Place prepared tart shells on a large baking sheet and bake for 10 minutes. Remove and allow to cool at room temperature.
Heat heavy cream in a small sauce pan or microwave until hot. Pour over chopped chocolate and allow to sit for 1-2 minutes to melt. Add sweetened condensed milk and whisk until smooth. Scoop 1tbsp of ganache into cooled tart shells and spread out evenly over the bottom. Reserve remaining ganache for drizzling. Refrigerate tart shells for 15-20 minutes to firm up ganache.
Beat cream cheese and peanut butter together until light and fluffy. Add icing sugar, sweetened condensed milk and vanilla. Beat until combined and smooth.
Beat heavy cream until stiff peaks form. Fold into peanut butter mixture. Scoop a full 1/4 cup of filling into each tart shell, smooth out the top as desired. Chill for at least an hour. Drizzle remaining ganache over tarts and garnish with shaved chocolate and/or chopped peanuts and serve.
You may need to warm the reserved ganache for drizzling. Simply microwave under medium power, whisking at 10 second intervals.