Mix together in a big bowl the water, oil, dry yeast and egg. Add the flour, sugar and salt. Knead a soft and smooth dough. Let the dough rise in a tray spread with a little oil for an hour or until the volume has doubled. From the raised dough, take out 12 equal parts, form balls and leave them covered with a kitchen towel to rise. Coat with egg and sprinkle with sesame seeds. Bake at 220° C for about 12 minutes. The ingredients for the burgers are mixed well to obtain a homogeneous mixture and left in the refrigerator for about 1 hour. Then form burgers the size of baked breads from the mixture. Fry in a preheated pan or grill on both sides for 7 minutes. After the burgers are fried, the burger buns are cut in half. Place the burger, a piece of yellow cheese, a leaf of fresh lettuce, tomato and onion on the bottom half of the bread and cover with the top half of the bread.