Preheat oven to 375 degrees F. Line a cookie sheet with Reynolds® Parchment Paper, set aside.
Beat butter and sugar until fluffy with an electric mixer. Mix in egg and lemon extract until well blended.
Combine flour, baking powder and salt in a separate bowl. Gradually beat flour mixture into butter mixture until smooth. Divide dough in half; shape into 2 flat disks. Wrap dough in parchment paper; refrigerate 1 hour until firm enough to roll.
Roll out the dough 1/8-inch thick between two sheets of lightly floured parchment paper.
Cut dough with 2 to 6-inch snowflake cookie cutters. Place cookies 1-inch apart on parchment-lined cookie sheet. Decorate with colored sprinkles.
Bake 8 to 10 minutes or until cookies are just beginning to brown on edges. Cool.
Mix powdered sugar and milk together in a small bowl, adding milk slowly until desired consistency is reached. Drizzle over cooled cookies.