1 cup (2 sticks) unsalted butter, room temperature
1/2 cup plus 1 tablespoon confectioners' sugar
2 1/2 cups all-purpose flour, plus more for work surface
Preheat oven to 300 degrees. Line two baking sheets with parchment paper; set aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar. With the mixer on low, slowly add flour. Continue mixing until dough comes together to form a ball.
Transfer dough to a lightly floured work surface; roll out dough to about 1/4-inch thickness, dusting rolling pin with flour as necessary to prevent sticking.
Here are 2 methods to form the cookies:
Using a 2 1/4-inch round, fluted cutter, cut out dough. Transfer to prepared baking sheet, spacing about 1 inch apart. Gather up any scraps, gently re-roll, and repeat cutting process. Take care not to overwork dough.
Transfer baking sheet to oven and bake until shortbread just begins to turn golden, about 30 minutes. Transfer cookies to a wire rack to cool. Shortbread may be stored in an airtight container for up to 3 days.
Knead well and divide dough into 2 equal portions. Press into 2 ungreased 8-inch round tart pans with removable bottom.
Bake 30-40 minutes or until golden.
Remove from oven, sprinkle lightly with sugar; cut into pie-shaped wedges. Store in airtight containers.