Sift dry ingredients together. Place in food processor and process a few seconds to mix. Cut each stick of butter into 8 pieces and place in food processor. Process 20 to 30 seconds until butter is cut in evenly. Add egg yolks and vanilla and process until mixture forms a ball. Remove, divide into 4 equal balls, flatten each and cover with plastic wrap. Refrigerate overnight.
Preheat over to 375 degrees. Cut aluminum foil to fit approximately 4 cookie sheets. Using a well floured pastry cloth and rolling pin cover, roll 1 section of dough, leaving the rest refrigerated until needed. Roll evenly approximately 1/8" thick (or actually 1/8" thin). Using small size cookies cutters, cut cookies (they should remain in the cutter, then tap out on to the foil lined cookie sheets). Place cookies 1/2 inch apart. Sprinkle with sugar crystals. (Easier to do one whole sheet red, next sheet green). Reroll scraps and roll out, trying to handle dough as little as possible. Don't reroll dough a third time, use another refrigerated section of dough. Bake approximately 8 minutes, one sheet at a time. Cookies should be slightly golden, remove quickly as once they start to brown, they could burn fast. Immediately slide foil off cookie sheet and leave cookies on foil to cool. Repeat with remaining dough. Store in a wax paper lined, cookie tin. Cookies reach their taste potential after a day and will stay fresh in a cookie tin approximatelly 3 weeks. Actual yield is based on the size cookie cutter used. I use a very small size, approximately 1 1/2 " across.