Preheat your oven to 350°F. While it heats, finely chop your nuts and set them aside in a small bowl. Measure out all your dry ingredients (flour and salt) into one bowl, and all your wet ingredients (softened butter, sourdough starter, and vanilla) into another. This preparation ensures smooth mixing and prevents scrambling to find ingredients mid-process.

In a large mixing bowl, combine the softened butter with 0.5 cup powdered sugar. Beat together until the mixture is light, fluffy, and pale in color—this usually takes 2-3 minutes with an electric mixer. This creaming process incorporates air into the dough, which helps create the tender, delicate crumb these cookies are known for.

Add the vanilla extract and sourdough starter discard to the butter-sugar mixture from Step 2. Mix until fully combined, scraping down the bowl as needed. The sourdough starter adds subtle tang and moisture while the vanilla provides aromatic depth. I find that active, bubbly starter works best here—it brings fermented complexity to what would otherwise be a straightforward butter cookie.

Add the dry ingredient mixture (flour and salt) from Step 1 to the wet mixture from Step 3. Mix on low speed just until the flour is fully incorporated—don't overmix. Fold in the chopped nuts until evenly distributed throughout the dough. The dough should come together into a soft, cohesive mass that holds together well.

Working with a tablespoon or small cookie scoop, roll the dough into uniform balls (about 1 inch diameter) and place them on a lined baking sheet, spacing them about 1 inch apart. Bake for 21-23 minutes until the edges are light golden brown but the centers still feel slightly soft to the touch. I like to slightly underbake these—they'll continue cooking from residual heat and stay wonderfully tender inside.

Remove the cookies from the oven and let them cool on the baking sheet for 2-3 minutes until they're cool enough to handle but still warm. Place the 0.75 cup powdered sugar for coating in a shallow bowl. Working in batches, roll each warm cookie in the powdered sugar until fully coated, then set aside on a wire rack to cool completely. Once cool, roll them in powdered sugar one more time for a thicker, more luxurious coating. This double-coating technique ensures an even, generous sugar shell.