Pre-heat oven to 325 degrees. Position the oven rack in the center of oven.

For the Pastry: In a medium mixing bowl, combine butter and cream cheese. Beat until smooth and creamy. Add flour; beat on low speed until combined. Shape dough into 24 balls. Press each ball evenly and up the sides of 24 ungreased mini muffin cups; set aside.

For the Filling: In a small saucepan, combine butterscotch chips, chocolate chips and butter. Heat and stir over low heat until melted. Remove from heat. Whisk in sugar and egg.

Spoon the chocolate butterscotch mixture evenly into the pastry shells, filling 2/3 of the way full.

Bake for 22-25 minutes or until the pastry is golden brown and the filling is puffed.

Remove the pan from the oven and let the tassies cool in the pan on a wire rack. Once cooled, carefully remove the tassies from the pan.

Place cookies between sheets of wax paper in an airtight container. Store at room temperature.