Source: Carol (Dishesdone)
This was Cookie of the Month in Martha Stewart Living.
1-1/2 cups (3 sticks) unsalted butter, softened, plus more for pan
2-1/2 cups all-purpose flour
1/2 teaspoon salt
3/4 teaspoon white peppercorns, coarsely ground
3/4 teaspoon black peppercorns, coarsely ground
3/4 teaspoon pink peppercorns, coarsely ground
3/4 teaspoon green peppercorns, coarsely ground
3/4 cup confectioners’ sugar
2 tablespoons granulated sugar
Preheat oven to 300°, with rack in center. Lightly butter a
10-inch springform pan, and set aside.
Stir together flour, salt, and 1/2 teaspoon of each ground
peppercorn; set aside. Put butter and confectioners’ sugar into
the bowl of an electric mixer fitted with the paddle attachment,
and mix on medium speed until fluffy, about 2 minutes, scraping
down sides of bowl as needed. Reduce speed to low. Gradually add
flour mixture, and mix until combined.
Using a small offset spatula, spread dough evenly into prepared
pan, smoothing top. Bake until shortbread is golden brown, about 1
hour 20 minutes.
Transfer pan to a wire rack. Immediately sprinkle with granulated
sugar and reserved 1/4 teaspoon of each ground peppercorn. Remove
springform; let shortbread cool completely. Cut into wedges.