Preheat your oven to 400°F and position a rack in the center. While the oven heats, remove the butter from the refrigerator if it hasn't already softened to room temperature—it should be soft enough to easily indent with your finger but not greasy or melted. Sift the 1.25 cups of confectioners sugar for coating into a shallow dish and set it aside; this removes any lumps and makes rolling easier. Measure out all remaining dry ingredients and have them ready for mixing.

In a large mixing bowl, cream together the softened butter and ½ cup confectioners sugar until the mixture is light, fluffy, and pale in color—this takes about 2-3 minutes of mixing and incorporates air that helps create tender cookies. Add the vanilla extract and mix until fully combined and fragrant. In a separate bowl, whisk together the flour and salt to distribute the salt evenly. Add the flour mixture to the butter mixture and stir until just combined; be careful not to overmix, as this can make the dough tough. I prefer to mix by hand at this stage so I can feel when the dough just comes together.

Cover the bowl of dough with plastic wrap or foil and refrigerate for 1 hour. This chilling time is essential—it allows the gluten to relax and the flavors to meld together, which results in cookies that hold their shape better during baking and have a more tender crumb. While the dough chills, you can clean up your workspace and prepare your baking sheets.

Remove the chilled dough from the refrigerator and break off pieces about the size of a walnut, rolling them between your palms into smooth 1-inch balls. Arrange the balls on parchment-lined or ungreased baking sheets, spacing them about 1 inch apart since they'll spread slightly. Bake for 8-10 minutes, watching until the bottoms are just barely golden but the tops remain pale—the cookies should look almost underbaked when you remove them from the oven. This is the key to keeping them tender and crumbly.

Let the cookies cool on the baking sheet for about 5 minutes—they'll firm up just enough to handle but will still be warm, which is crucial. Working quickly while they're still warm, gently roll each cookie in the prepared confectioners sugar, coating all sides generously. I like to work in small batches so the cookies stay warm and the sugar adheres properly. Transfer the coated cookies to a wire rack to cool completely. If you want an extra-thick sugar coating, you can roll the cookies in sugar a second time once they've cooled.