Gilded Sesame Cookies

Whisk together flour, baking powder, and salt in a small bowl.

Beat together butter and sugar in a large bowl with an electric mixer at medium-high speed until pale and fluffy, about 3 minutes, then beat in tahini and vanilla. Reduce speed to low and add flour mixture in 2 batches, mixing until a crumbly dough forms.

Transfer dough to a sheet of plastic wrap and press into a disk. Chill dough, wrapped in plastic wrap, until firm, at least 1 hour.

Put oven racks in upper and lower thirds of oven and preheat oven to 350°F. Line 2 large baking sheets with parchment paper.

Stir together sesame seeds and luster dust (if using) in a small bowl.

Roll dough into 1-inch balls, then roll balls 1 at a time in seeds to coat and arrange 2 inches apart on lined baking sheets.

Bake, switching position of sheets halfway through baking, until cookies are puffed and starting to crack, 12 to 15 minutes total. Cool on sheets 10 minutes (cookies will be very fragile when hot), then transfer from parchment to a rack to cool completely.

•For this cookie, it's best to use hulled sesame seeds, found at most supermarkets. They're not usually labeled "hulled"; look for sesame seeds that are pale ivory in color and more delicate than the mottled beige ones, which still have their outer coating and are found at natural foods stores and Asian markets.•Dough can be chilled up to 1 day.•Cookies keep in an airtight container at room temperature 5 days.•Luster dust is nontoxic. However, the FDA recommends that it be used for decorative purposes only. If you want to use a coloring that is entirely safe (though not available in gold or silver) try Crystal Colors at sugarpaste.com. The colors are great for kids.