Heat oven to 400°F. Remove pie crusts from pouches; unroll on work surface. Flatten slightly with rolling pin. Using 3-inch round cutter, cut out 12 rounds from each crust. Invert mini muffin pan. Place crust rounds on backs of 24 cups, pressing and pinching to form cup. Bake 12 to 15 minutes or until light golden brown. Reduce oven temperature to 350°F.
Meanwhile, in 2-quart saucepan, heat pudding mix and milk to boiling over medium heat; boil 1 minute. Remove from heat; stir in chopped chocolate.
Place baked shells inside mini muffin cups in pans (they will not fit, but will sit toward the top and keep crusts from tipping). Spoon slightly less than 2 tablespoons pudding into each cup.
In medium bowl, beat egg whites, cream of tartar and vanilla with electric mixer on medium speed about 1 minute or until soft peaks form. Gradually add sugar, 1 tablespoon at a time, beating on high speed until stiff glossy peaks form and sugar is dissolved. Fold in grated chocolate. Spoon meringue onto pudding in each cup; spread to edge of crust to seal well and prevent shrinkage.
Bake 10 to 15 minutes or until meringue is light golden brown. Cool completely, about 1 hour. Refrigerate until filling is set, about 1 hour. Store in refrigerator.