1. Preheat the oven to 350°F (175°C) and line two large baking sheets with parchment paper or silicone baking mats so the cookies bake evenly and don’t stick.

2. In a medium bowl whisk together the all-purpose flour, baking powder, baking soda, and salt until everything is evenly combined, then set the bowl aside.

3. In a large mixing bowl beat the softened butter, granulated sugar, and 1/2 cup powdered sugar together with a hand mixer or stand mixer on medium speed for 2–3 minutes, until the mixture is light, creamy, and slightly paler in color.

4. Add the egg, egg yolk, and vanilla extract to the butter mixture and beat again until the mixture looks smooth and glossy and no streaks of egg remain.

5. Add the dry ingredients to the wet ingredients in two additions, mixing on low speed just until the flour disappears; if the dough looks dry or crumbly, mix in the milk or cream 1 tablespoon at a time until you have a soft, scoopable dough.

6. Pour 3/4 cup powdered sugar into a shallow bowl. Scoop the dough into 1 to 1 1/2 tablespoon portions, roll each portion into a smooth ball between your palms, then roll the dough ball in the powdered sugar to coat completely.

7. Place the coated dough balls on the prepared baking sheets, spacing them about 2 inches apart so they have room to spread slightly while baking.

8. Bake the cookies for 9–11 minutes, or until the edges look set and the tops are just beginning to crack; the centers should still look soft and slightly underbaked.

9. Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely; once cool, sift additional powdered sugar over the tops and decorate with sprinkles if desired.

10. Store the cooled cookies in an airtight container at room temperature for up to 4–5 days, or freeze them for longer storage and dust with a fresh sprinkle of powdered sugar just before serving.