To make the dough with an electric mixer, in the mixer bowl, combine the butter, sugar and salt.
Beat on medium speed until smooth. Reduce the speed to low, add the egg yolks and vanilla and beat until blended.
Add the flour and beat until incorporated and a smooth dough forms.
Divide the dough into 4 equal portions. Roll out each portion into a log 7 inches long and about 1 1/2 inches in diameter.
Wrap the logs in plastic wrap and refrigerate until firm, at least 2 hours.
Preheat an oven to 350°F
Line 3 rimless baking sheets with parchment paper.Using a sharp knife, cut each unwrapped log crosswise into slices 1/4 inch thick.
Place the cookies 1 inch apart on the prepared baking sheets.
Bake the cookies, 1 sheet at a time, until the edges and bottoms are golden, 12 to 15 minutes.
Let the cookies cool on the baking sheets for 5 minutes, then transfer them to wire racks and let cool completely.