Fill bowl of electric mixer with warm water and let stand for 2 to 3 minutes. Empty the water and wipe with a dry kitchen towel. Using the paddle attachment, starting on low speed, cream the butter until smooth, about 1 to 2 minutes, scraping down the side of the bowl as needed. Add the sugar and continue to mix until well blended, about 2 minutes. Reduce the speed to low, add the flour and mix just until the mixture forms a soft dough. In a small mixing bowl, whisk together the egg yolks and vanilla extract. Add them to the butter mixture, mixing on medium speed for about 1 minute and scraping the sides of the bowl. Mix half the flour into the butter mixture, mixing on medium speed for about 1 minute, then add the remaining half and mix until just combined, about 1 more minute. Remove the dough from the electric mixer, wrap in plastic and refrigerate until firm, about 1 hour. Line 2 baking sheets with parchment paper. Divide the dough into 4 equal pieces and work with one at a time, keeping the others refrigerated. Lightly dust a work surface with flour. Turn one piece of dough out on the work surface. Dust your hands or a rolling pin with flour and flatten or roll the dough to about 3/8" thick. Using a cookie cutter, cut out the cookies and place them about 1" apart on the parchment-lined baking sheets. Repeat with the remaining pieces of dough. Gather the scraps together into a loose ball, refrigerate until firm, about 1 hour and reroll. Preheat oven to 325°F. Bake the cookies until they are firm to the touch and lightly golden brown, about 12 to 15 minutes.