Preparation

Sieve the flour onto a board, make a hole in the middle of it and add the oil into the hole. Gradually create a paste by adding water into which you put salt and vinegar. Then continue to knead for 10 minutes until smooth. Divide it into four parts, knead and round them, put on a board sprinkled with flour, coat with oil and cover with a larger bowl. Let the dough rest for 30 minutes.

Roll the pastry with a roller on board, brush with oil, and then slightly stretch  it with the upper parts of the hand into a circle. Put it on the table cloth and stretch with your hands (not fingers) until it becomes thin and transparent. Cut thick edges and sprinkle the surface of the pastry with 2-3 tablespoons of oil.

Arrange a quarter of the squash, sprinkle with a tablespoon of semolina, a fourth of the amount of sugar and a teaspoon of cinnamon. On three sides, fold the edges of the dough, and start rolling the pastry a bit wider on the other side where the stuffing is. Place a strudel in a greased baking pan and repeat the process with the rest of the pastry and filling.

Coat the strudel with a mixture of sour cream and egg and bake in a preheated oven at 180°C (350°F) for about 40 minutes.