Heat oven to 350 F.
Unroll piecrusts onto a lightly floured surface. Carefully roll into two 15-inch circles. Working with one crust at a time, cut out 20 to 22 circles using a 2-3/4-inch round cookie cutter, re-rolling dough as needed. Place in 1-3/4-inch mini-muffin pans, pressing on bottom and up sides of each mini-muffin cup (coat with nonstick cooking spray if pan is not nonstick).
Combine melted butter, brown sugar, flour and eggs in a large bowl, mixing well. Add vanilla. Stir in pecans and toffee bits.
Spoon pecan filling evenly into pie shells (a scant tablespoon filling per mini-muffin cup). Bake at 350 F for 20 minutes, or until filling is set and crust is lightly browned. (This can be done in batches, if you only have one pan.) Cool slightly in pans on wire racks; transfer directly to racks to cool completely. Dust with confectioners sugar before serving. A scant 4 dozen pieces.