Dissolve citric acid and salt in water, add an egg and wheat flour (reserving 2 tablespoons) and knead the dough until a smooth ball is formed. Cover the ball with cloth and leave for 20-30 minutes to develop gluten.

Cut the butter into small pieces, add 2 tablespoons flour and chop to get crumbly texture. Shape a square out of the butter mix 0.8 inch (2cm) thick and refrigerate.

Dust the working surface with flour. Roll out the dough into a rectangle Place the softened square of butter on the center of the dough. Lift each end of the dough over the butter and seal like an envelope. Now roll the dough in one direction into a rectangle again, brush off any excess flour from the surface of the dough. Bring both ends toward the center like a book. Then, fold in half, closing the book. Now we have 4 layers. Dust the dough with flour and refrigerate for 30-40 min.

Then brush off excess flour, roll out the dough again into a rectangle, fold in half 2 times and refrigerate. Repeat this operation once again. 30 minutes later the dough can be prepared.