Here's the recipe from Martha Stewart:
Ingredients: Makes 2 dozen
2 cups all-purpose flour
1/4 teaspoon salt
1/2 teaspoon baking powder
1/2 cup (1 stick) unsalted butter
1 cup sugar
1 large egg, lightly beaten
2 tablespoons brandy, or milk
1/2 teaspoon pure vanilla extract
Royal Icing for Sugar Cookies, optional
1. Whisk together flour, salt, and baking powder in a medium bowl; set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar; mix until light and fluffy. With mixer running, add egg, brandy, and vanilla; mix until well combined. With the mixer on low, slowly add reserved flour mixture. Mix until just combined.
2. Transfer dough to a work surface. Shape into 2 discs, cover with plastic wrap, and refrigerate for at least 1 hour.
3. Preheat oven to 350 degrees. Line baking sheets with nonstick baking mats or parchment paper; set aside.
4. On a lightly floured work surface, roll out dough to 1/8-inch thickness. Cut into desired shapes, and transfer to prepared baking sheets, leaving an inch in between. Leftover dough can be rolled and cut once more. Bake until lightly golden, about 10 minutes; do not allow to brown. Transfer to wire racks to cool.
5. Decorate with Royal Icing, optional.