For the dough, dissolve the sugar and yeast in 1 glass of milk. Beat the egg and salt and add the fermented milk and 2 glasses of milk. Prepare a custard-like dough by adding flour to the milk. Let the dough rest for 30 minutes. For the syrup, boil water and sugar, add slices of lemon, turn off the heat and leave to cool. Mix cinnamon sugar and walnuts for the inside. Pour the dough into the hot pan with a small ladle and cook until one side is eye-to-eye. Before the baked dough cools down (it won't stick if it gets cold), add the walnut stuffing and close the edges. Cook both sides in hot oil and drop into cold syrup. Serve after 1 hour.