Unroll pie crusts on work surface. With rolling pin, roll each crust lightly into 12-inch round.
With 3-inch round cutter, cut 24 rounds from crusts, re-rolling scraps as necessary.
Press 1 pie crust round in bottom and up side in each of 24 ungreased mini muffin cups, so edges of crusts extend slightly above sides of cups. Bake 5 to 7 minutes or until very light golden brown; cool.
Reduce oven temperature to 325 degrees.
Cut candy bars in half lengthwise; cut into 1/8-inch pieces; chop coarsely. Place candy bar pieces in bottoms of cooled crust-lined cups, reserving some for garnish.
In small bowl, beat cream cheese and sugar with electric mixer on medium speed until smooth.
Beat in egg until well balanced.
Add sour cream and peanut butter, beating until mixture is smooth.
Spoon 2 teaspoons cream cheese mixture over candy bar pieces in each tart.
Bake at 325°F for 15 to 20 minutes or until center is set.
Cool completely (about 30 minutes).
In pyrex measuring cup, place whipping cream.
Heat in microwave until bubbling.
Remove and stir in chocolate chips until melted and smooth.
If necessary, return to microwave for 30 seconds until hot enough to melt. DON’T OVERHEAT.
Place a dollop of chocolate ganache on top of each tart.