Buckwheat Butter Cookies with Cacao Nibs

Whisk the flours together in a medium bowl. Set aside. In another bowl, with the back of a large spoon or with an electric mixer, beat the butter with the sugar and salt for about 1 minute, until smooth and creamy but not fluffy. Mix in the nibs and vanilla. Add the flours and mix just until incorporated. Scrape the dough into a mass and, if necessary, knead it with your hands a few times, just until smooth.

Form the dough into a 12- by 2-inch log. Wrap and refrigerate for at least 2 hours, or preferably overnight.

Position the oven racks in the upper and lower thirds of the oven and preheat the oven to 350° F. Line two baking sheets with parchment paper.

Use a sharp knife to cut the cold dough log into 1/4-inch-thick slices. Place the cookies at least 1 1/2 inches apart on the baking sheets. (You also may roll out the dough and cut with a cookie cutter.)

Bake until the cookies are just beginning to color at the edges, 12 to 14 minutes, rotating the baking sheets from top to bottom and front to back halfway through the baking. The cookies are delicious fresh but even better the next day. They can be stored in an airtight container for at least 1 month.