Mix all the dry ingredients—flour, sugar, pinch of salt, and walnuts—in a large bowl. Add the vanilla extract. Add the butter in little pieces, and combine everything together with clean hands until the mixture looks like a coarse meal with nut bits in it.

Chill the dough for at least 30 minutes in the fridge or up to overnight.

Preheat the oven to 300°F. Line a baking sheet with parchment or silicon baking mats.

Form the dough into small balls no larger than a walnut and place them on the cookie sheet, spaced at least an inch apart from each other.

Bake the cookies for 35 minutes.

When cookies are still warm but cool enough to touch, roll them in the powdered sugar. Set aside on a rack to cool completely. When cool, dust again with powdered sugar.