In a medium bowl, combine the 1/2 cup butter and cream cheese. Beat with an electric mixer on medium to high speed until combined. Add flour. Beat on low speed just until combined. Cover and chill for 30 to 60 minutes or until dough is easy to handle.

Preheat oven to 325 degrees F. Shape dough into 24 balls. Press each ball evenly into the bottoms and up the sides of 24 ungreased 1-3/4-inch muffin cups; set aside.

In a small saucepan, combine butterscotch pieces, semisweet chocolate pieces, and 2 tablespoons butter; heat and stir over low heat until melted. Remove from heat. Whisk in sugar and egg. Spoon butterscotch mixture evenly into the pastry-lined cups.

Bake in the preheated oven for 20 to 25 minutes or until filling is puffed and pastry is golden brown. Cool tassies in pan on a wire rack for 5 minutes. (Filling will fall slightly as it cools.) Run a thin knife or thin metal spatula around the edge of each tassie and carefully remove from the muffin cup. Transfer tassies to a wire rack; let cool. Drizzle with Butterscotch Drizzle. Makes 24 tassies.

In a small saucepan, combine 1/4 cup butterscotch pieces and 2 teaspoons shortening; heat and stir over low heat until melted.

Place cookies between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to three days or freeze for up to 3 months.