1. Mix the butter using an electric mixer or the paddle attachment on a stand mixer and gradually add the sugar. Beat at a medium speed until light in color and fluffy in texture. Add the kosher salt, yolks, one at a time, and vanilla extract. Continue beating until well incorporated. Add the flour, and beat using a low speed until the flour is just mixed in. Divide the dough in 2 balls, wrap in plastic wrap. If desired, roll each ball out to a 1/4 inch thickness before placing in the refrigerator. Do this between two layers of plastic wrap, using a rolling pin on top of the dough sandwiched between the two layers of plastic wrap. Refrigerate until firm, at least an hour
2. Place oven racks in the middle and lower middle of the oven and preheat the oven to 350°
3. Remove one sheet of dough from the refrigerator (allow to soften for a few minutes at room temperature if it comes directly from freezer). Keep the bottom of the plastic wrap in tact, but remove the top piece. Cut dough into desired shapes. Remove from wrap using a spatula, or picking up the wrap slightly, bending to pry off cookie. If the dough is very sticky, lightly dust with flour to prevent sticking
4. Place cookies ½" apart on a parchment-lined (or Silpat lined) baking sheet. Bake, and rotate the cookie sheets halfway though baking if your oven is uneven.  Switch the racks if cookies are baking unevenly.They should be a light golden brown,  around the outside edges, about 15-20 minutes, depending on how many sheets are in the oven. The raw scraps can be re-rolled, chilled and reused once or twice, at which point the dough becomes too oily to use (but are still tasty as a snack when baked)
5. Using a thin-bladed spatula, immediately transfer the cookies to a cooling rack. Cool completely before icing. If you are making a cookie bouquet, while the cookies are still  hot, place the pointed end of a skewer or a lollypop-style stick into the base of the cookie. Keep one hand on top of the cookie to guide and prevent the skewer from poking through the top of the cookie.  Any small cracks can be quickly pinched closed around the skewer while the cookie is still hot.  If too hot to touch, use a paper towel between your hand and the cookie. Allow to cool to room temperature. Store decorated or undecorated in an airtight container for up to three weeks.  If  small children will be eating the cookies from a cookie bouquet, be sure to take the stick out before they eat the cookie, or use blunt ended skewers to prevent injury

Note: Dough can be made ahead. It will keep three days in the refrigerator, or tightly, doubly wrapped, three months in the freezer. Consider working with your dough in frozen sheets, especially if your kitchen is very warm, or the dough is on the sticky side. Frozen dough is easier to work with especially cutting very simple shapes