On a surface covered with the all purpose flour, roll out your pie crust. Cut out 3-inch circles (with a cookie cutter or drinking glass) of the rolled-out dough and place each pie circle in a the greased mini pie tin.
Make your filling. In a medium-sized bowl, mix blueberries, cornstarch, sugar, and lemon. Fill each pie crust with your blueberry mixture and dot the top of it with small pats of butter.
Bake for about 15 to 18 minutes or until pie crust is golden brown. Allow the pies to cool on a rack for 10-15 minutes before serving.