In a large bowl mix flour, yeast, salt and sugar. Using a Pastry Cutter (like this affiliate) to cut the butter into the dry mix. It will still be lumpy. Add ¾ cups sour cream and yokes. Combine until dough mostly sticks together. Add more sour cream bit by bit, if needed. Make a ball with the dough. Divide and roll dough into 8 equal balls. Wrap each ball in plastic wrap and store in the refrigerator over night. Dough can be stored up to 4 days.
Cover your rolling surface with a dusting of sifted powder sugar. Take one ball out of the refrigerator and start rolling out the dough by pushing down in the center of the ball with a rolling pin. Turn ¼ turn, and push out from the center again. Turn ¼ turn and push out from the center, but don't roll out to the edges. This will create uneven edges. Continue pressing from the center out and then turning ¼ turn. Occasionally sprinkling the dough with sprinkling If edges start to crack form the dough back together. Roll dough to about ⅛ inch thick.
Using a pizza cutter, divide dough into 8 equal triangular segments. Place about 1 teaspoon pastry filling at the large end of the triangle. Roll starting from the large end, over the filling. Place kolacky on a parchment lined baking sheet. Be sure that the small end or tip of the roll is under the cookie. This will prevent it from popping up while baking.
Bake at 350 for 12 -16 minutes until the cookie is has browned. Remove cookies and let cool. Sprinkle more powder sugar on top. If you're not going to serve the day of, store in an air tight container in the freezer.
Recipe by Culinary Mamas at https://culinarymamas.com/kolacky-polish-cookies/