Cream the butter and sugar together in a large bowl with your mixer on high, scraping down the sides of the bowl occasionally. The mixture is creamed when the sugar is well incorporated into the butter.
Beat in the egg yolks, salt, and vanilla.
When the mixture is well combined add the flour one cup at a time and stir. You can use the lowest setting on your electric mixer or do this part by hand. (I'm lazy, I use my mixer!) Make sure the flour is completely incorporated.
Divide the dough into 3 equal pieces and form each piece into a 1-inch in diameter log. Wrap each log in plastic wrap and refrigerate for a minimum of one hour or up to 3 days. (Or freeze, see Gr8 Note.)
Preheat your oven to 350°F.
Remove one log from the refrigerator and slice at ½-inch intervals. Place on cookie sheet at least an inch apart.
Bake for 11-14 minutes until the edges are golden brown.