Prepare 12 large crepes about 10-12 inches in size.
For the filling, combine the farmer's cheese, butter, sugar, and egg yolk. Stir the mixture until smooth.
Place a dollop of the cheese filling on the bottom part of each crepe, leaving enough room on the edges for folding.
Fold over both of the sides.
Starting from the bottom, roll up the crepes and secure the filling inside.
Keep the blintzes refrigerated until you're ready to serve them. Right before serving, warm them up on both sides in a skillet with butter over medium heat. Enjoy!