Storage: Store in an airtight container at room temperature for 3–4 days, layered with parchment to prevent sticking. To freeze, place cookies on a tray to freeze solid, then transfer to a freezer-safe container for up to 2 months.
Variations: Use milk or dark chocolate chips, add a teaspoon of espresso powder to the dough, or stir pecans into the glaze. No buttermilk? Substitute 3 tbsp milk plus 1 tsp lemon juice or vinegar, and let stand 5 minutes.