1. Beat 1 cup butter and cream cheese at medium speed with an electric mixer until creamy. Gradually add flour to butter mixture, beating at low speed. Shape mixture into 48 balls, and place on a baking sheet; cover and chill 1 hour.
2. Place 1 dough ball into each lightly greased muffin cup in mini muffin pans, shaping each into a shell.
3. Whisk together brown sugar and next 5 ingredients. Spoon into tart shells.
4. Bake at 350° for 20 minutes or until filling is set. Cool in pans on wire racks 10 minutes. Remove from pans; cool on wire racks 20 minutes or until completely cool.
Prep: 45 min., Chill: 1 hr., Bake: 20 min., Cool: 30 min. If you don't have four mini muffin pans, you can bake these in batches. Keep the extra dough chilled until you're ready to use it.