These are meant for New Year's. With the spiciness of cloves and the soft citrus-y hint of cognac, these cookies crumble as you eat them in a way that, for whatever reason, bodes well for the year to come.
Preheat the oven to 300 degrees.
To grind the walnuts, combine the nuts and 2 tablespoons of flour in a food processor. Pulse until the nuts are finely ground, not pasty. Set aside.
In a mixer, beat butter and confectioners’ sugar for 1 minute, until fluffy. Add the egg yolk, brandy, and clove. Beat in remaining flour and walnuts just until mixed — don't overmix.
Shape a scant tablespoon of dough in a ball. Flatten it out and elongate the ends slightly. Set on a parchment-lined baking sheet. Bake 12-16 minutes, until the cookies are firm but colored only on the bottom. Remove the tray and set it on a rack.
Sift a coat of confectioners’ sugar all over the hot cookies. Let cool for about 15 minutes, and then add a second coat of sugar. Let cool completely. Keep in an airtight container.