For a Saint Patrick's Day-themed treat, sprinkle a little luck on your sugar cookies with some decorative clovers.
Sift flour, salt, and baking powder into a large bowl, and set aside. Put butter and granulated sugar in the bowl of an electric mixer fitted with the paddle attachment; cream on high speed until fluffy. Beat in eggs.
Reduce speed to low. Add flour mixture in two additions, and mix until well combined. Mix in vanilla. Divide the dough in half, and wrap in plastic wrap; refrigerate 30 minutes.
Preheat oven to 350 degrees. Sift together confectioners' sugar and food coloring into a small bowl, and set aside.
Roll out 1 piece of dough on a lightly floured work surface 1/8 inch thick. With a 2 1/2-inch cookie cutter, cut out 25 rounds. Arrange rounds on parchment-lined baking sheets 2 inches apart.
Working with one round at a time, place clover stencil on top; using a small sieve, sprinkle surface with green sugar. Refrigerate until firm, about 15 minutes, or until ready to bake. Repeat process with remaining dough.
Bake, one sheet at a time, until edges just start to brown, 10 to 12 minutes. Let cool completely on sheets on wire racks.
You can freeze the dough, wrapped in plastic wrap, for up to one month. Store the cookies in an airtight container up to five days.