Step 1

Melt 2 sticks butter in a small skillet over medium heat. Cook, stirring often with a rubber spatula, until butter foams, starts to smell nutty, and the milk solids—the sandy bits at the bottom of the pan underneath the liquid butter—are turning golden brown, 6–8 minutes. Don’t walk away; the butter can go from perfectly golden to burnt very quickly! Once butter is golden, immediately pour it into a large heatproof bowl (it will keep cooking if you leave it in the pan) and chill until starting to solidify, about 30 minutes. That's brown butter, people! That's all it is!

Step 2

Meanwhile, very finely chop 1 cup walnuts (they should be about the size of a lentil). Don't like walnuts? Any nut will be delicious here.

Step 3

Add ½ tsp. salt and ½ cup powdered sugar to bowl with butter. (If you've ever been tempted to leave salt out of a baking recipe, DON'T—you can't taste the sweet properly without a bit of salt.) Using an electric mixer on high speed, beat until mixture is lightened in color and very fluffy, about 3 minutes.

Step 4

Scrape down sides of the bowl with rubber spatula. Add 2 cups flour and beat on low speed until dough is thick and smooth.

Step 5

Using rubber spatula, fold chopped nuts and 1 tsp. vanilla into batter, scraping bottom and sides of bowl, until incorporated. (Swapping the vanilla extract for almond or orange extract would be fun, too.) Cover bowl with plastic and chill dough until firm, about 1 hour.

Step 6

Place a rack in middle of oven; preheat to 325°. Line a rimmed baking sheet with parchment paper. A note about parchment paper. It's a great thing to have for baking situations such as these—it is essentially nonstick, and makes cleanup a breeze—but if for whatever reason you forgot to buy it, you can always grease your baking sheets well and bake directly on the metal; the cookies might brown a little more quickly, so keep an eye on them. Also: Under NO CIRCUMSTANCES can you substitute wax paper for parchment! Roll dough into 1" balls and arrange on prepared pan.

Step 7

Bake cookies, rotating pan halfway through, until firm and beginning to look dry but haven’t taken on any color, 20–22 minutes. Let cookies cool on sheet until they're just cool enough to handle but still warm.

Step 8

Sift remaining 1 cup powdered sugar into a large bowl. Toss warm cookies in powdered sugar. Transfer cookies to a wire rack and let cool completely. Toss one more time in powdered sugar.

Step 9

The cookies are best if you have some patience—store them in an airtight container and let them sit out at room temperature overnight. They're best after they've sat for a bit...but they also definitely don't suck when they're still warm.

Step 10

Do Ahead: Cookies can be made 5 days ahead. Transfer to an airtight container and store at room temperature.