Instructions:

1. Adjust oven rack to middle position; heat oven to 375 degrees. In small bowl, beat yolk, cream, and vanilla with fork until combined; set aside.
   
   
2. In standing mixer, cream butter, sugar, and salt at medium-high speed until light and fluffy, 3 to 4 minutes. Scrape down bowl with rubber spatula. With mixer running at medium speed, add yolk/cream mixture and beat until incorporated, about 30 seconds. Scrape down bowl. With mixer running at low speed, gradually beat in flour until combined. Scrape down bowl and give final stir with rubber spatula to ensure that no flour pockets remain.
   
   
3. If using cookie press to form cookies, follow manufacturer's instructions to fill press; if using pastry bag, follow illustrations 1 through 3 below to fill bag. Press or pipe cookies onto ungreased baking sheets, spacing them about 1-½ inches apart. Bake one sheet at a time until cookies are light golden brown, 10 to 12 minutes, rotating baking sheet halfway through baking time.
   
   
4. Cool cookies on baking sheet until just warm, 10 to 15 minutes; using metal spatula, transfer to wire rack and cool to room temperature.