In a medium size bowl combine: egg yolks, sour cream, vinegar, vanilla and lemon zest. Using a hand whisk or a mixer combine all until smooth.
In a large mixing bowl combine flour with two tsp of the powdered sugar. Slowly add the egg yolk mixture.
Transfer all to a stand mixer bowl with the dough hook attached
Mix on low speed until the dough comes together. (about 5-7 minutes). You can also knead the dough by hand.
Transfer the dough into a lightly floured, flat surface. Roll it out slightly. Fold it in half and over in half again.
Beat, yes, beat the dough with the rolling pin. Don't hold back :) Why? This action will create air pockets, lots of them. Why are air pockets important? They will give the crust this airy, light crispy texture.
You can repeat the rolling out and folding a few times. It will create lots of air pockets that will contribute to a wonderfully airy dough.
After all that rolling and beating you both will need some rest. Wrap the dough in plastic wrap or cover with towel and let it rest for 15-20 minutes
When ready, cut the dough in half or in quarters, for easier rolling. On a lightly floured surface roll out the dough. It must be thin!, almost paper thin.
Cut the dough into about 1.5 inches wide strips; cut each strip into 3 to 5 inches long pieces and finally make a small cut in the middle of each strip.
To assemble the chrusciki, pick both of the ends and fold one of them through the cut in the middle. They should look like twisted ribbons :)
While you rolling the last piece of dough, fill a cooking pan with at least 2-3 inches of cooking oil
Preheat the oil to 350F
Place a couple of paper towels on a large baking sheet. You will use it to set the cooked chrusciki on to drain some of the oil off.
Gently place the chrusciki in batches into the hot oil. Don't crowd the pan, you need to be able to maneuver the cooking chrusciki around.
Watch carefully as they cook. You need to flip them over when the bottom side becomes lightly brown. They cook quickly. Make sure you have tools ready to help you with the flipping.
When fully cooked place them on the baking sheet with paper towels
After the chrusciki cool slightly dust them with powdered sugar
They are best enjoyed the same day
Notes
Use chilled ingredients, they will create flakier crust
Kneading - multiple times and different ways, folding, and rolling
Rest - let the dough rest at least 30 min
Roll - real thin!
Oil temperature - bring it to and maintain throughout the cooking at 350F-375F