Beat butter and cream cheese in a bowl until smooth. Add flour; beat just until a soft dough forms. Form into a ball and wrap in plastic wrap; chill for 1 hour or overnight.
Preheat oven to 425 degrees F/220°C.
Shape dough into 1"/2.5 cm balls. Place each ball of dough into cups of mini muffin pan. Dip Mini-Tart Shaper into flour; press into dough to form tart shells. Pierce shells with a fork. (If you don't have a Mini-Tart shaper just use your fingers and form into shells).
Bake 10-12 minutes or until light golden brown. Cool in pan for 5 minutes; carefully remove tart shells from pan. Cool completely. Fill as desired.