German Spice Cookies (Pfeffernusse)

Cookies: Preheat oven to 350 degrees. Line three baking sheets with parchment paper.

In a medium bowl, combine flour, baking soda, and spices. Set aside.

In the bowl of an electric mixer fitted with the paddle attachment, beat together butter, brown sugar, and molasses on medium speed until fluffy, about 3 minutes. Beat in egg and vanilla. With mixer on low speed, add flour mixture; beat until just combined. Pinch off a heaping teaspoon of dough, roll into a ball, and place on a prepared baking sheet. Repeat process with remaining dough, spacing balls 1 1/2 inches apart. (Dough can be frozen at this point, covered tightly with plastic wrap, up to 1 month.)

Bake, rotating sheets halfway through, until cookies are golden and firm to the touch with slight cracking, about 15 minutes. Transfer sheets to a wire rack to cool completely.

Glaze: Fit a rimmed baking sheet with a wire rack. In a medium bowl, whisk together confectioners' sugar, milk, and kirsch, if desired. Using a fork, dip each cookie in glaze to coat. Tap to remove excess glaze and place on wire rack to dry. Repeat with remaining cookies.

To decorate: While the glaze is still wet, top cookies with a small pinch of peppercorns, if desired. Alternatively, let glaze dry completely before mixing together luster dust and kirsch with a small paintbrush. Lightly brush tops of cookies with luster dust mixture, if desired. Let dry before serving. Cookies can be stored in an airtight container at room temperature up to 2 weeks.