1. In a bowl, beat butter and powdered sugar until light and fluffy (~2 min).
2. Mix in egg yolk and vanilla until smooth.
3. Gently fold in flour and salt until just combined—do not overmix. Dough should be soft but hold shape. Chill 15–20 min if too soft.
4. Load dough into a cookie press fitted with your favorite disc (stars, wreaths, etc.). Press onto ungreased baking sheets, spacing 1½ inches apart.
5. Add sprinkles lightly (they adhere best before baking).
6. Bake at 350°F (175°C) for 10–12 min—edges should be just golden; centers pale. Cool on sheet 2 min, then transfer to rack.

PREP TIME & NUTRITION (per cookie, makes ~36):
Prep Time: 20 min | Cook Time: 12 min | Total Time: 35 min (incl. chill) | Servings: 36 | Calories: 65 | Net Carbs: 6g | Fats: 4.5g | Protein: 1g