Preheat oven to 350°F. For tart shells, beat butter and cream cheese inClassic Batter Bowluntil well blended. Add flour; mix until a soft dough forms.
UsingSmall Scoop, shape dough into 1-inch balls. Place balls of dough into ungreased cups ofDeluxe Mini-Muffin Pan. DipMini-Tart Shaperin flour; press into dough with even pressure until dough rises slightly above rim of pan.
For filling, place butter inSmall Batter Bowl; microwave on HIGH 30 seconds or until melted. Stir in brown sugar, egg and vanilla. Finely chop pecans usingFood Chopper; add to batter bowl and mix well.
Using Small Scoop, fill each tart shell with level scoop of filling (do not overfill). Bake 20-25 minutes or until light golden brown. Remove from oven; cool in pan 3 minutes. Remove from pan toStackable Cooling Rack; cool completely. Sprinkle with powdered sugar, if desired.