Preheat the oven to 350ºF. (180ºC). Place four 4-inch tart pans with removable bottoms* on a baking sheet.
In a medium-size bowl, mix the crushed sandwich cookies with the melted butter until well combined. Press the crumb mixture into the tart pans.
Bake for 8 minutes. Let cool completely.
Filling
In a medium-size bowl, beat the peanut butter and softened butter until smooth. Add the remaining filling ingredients and beat until smooth and well combined.
Fill the cooled tart shells with the filling. Refrigerate the tarts until set, at least 2 hours.
Topping
Place the chopped chocolate in a small bowl.
In a small saucepan, heat the heavy cream over medium-low heat just until bubbles form around the edges. Do not boil. Pour the hot cream over the chocolate. Let sit two minutes then stir until smooth.
Spoon over the peanut butter filling. Add toppings if desired. Refrigerate until chocolate is set. Carefully remove tarts from pans.