How to Make It
Preheat the oven to 350°. Line 2 large cookie sheets with parchment paper. Spread the walnuts on a rimmed baking sheet and bake for about 8 minutes, until golden brown. Let cool, then coarsely chop. Reduce the oven temperature to 325°.
In a standing mixer fitted with the paddle, beat the butter with the vanilla bean seeds at high speed until pale, about 2 minutes. Add 1 cup of the confectioners’ sugar and beat at medium-high speed until light and fluffy, about 5 minutes, scraping down the side of the bowl with a rubber spatula halfway through. At low speed, mix in the salt, then gradually add the flour and walnuts and beat just until the cookie dough comes together, scraping down the side of the bowl halfway through.
Roll level tablespoons of the dough into balls and arrange them on the prepared cookie sheets. Bake the cookies in the upper and lower thirds of the oven for about 17 minutes, until they are lightly browned on the bottom; switch the sheets from top to bottom and front to back halfway through baking. Let the cookies firm up on the sheets, about 5 minutes, then transfer them to a rack to cool slightly.
Put the remaining 1 cup of confectioners’ sugar in a small bowl. Roll the warm cookies in the sugar to coat and return to the rack to cool completely. Roll again in the sugar.