On a pastry board, pour flour and shape it into a mound. Press down the center of the mound to form a cup shaped hole.
Into the hole put the olive oil, salt, and water and bring the sides of the mound together toward the center, thoroughly mixing all ingredients.
Knead dough 5-6 mins, then form into a ball and put it aside to rest between two soup plates. Let it rest for about hours.
Prepare the filling, mixing the three cheeses in a bowl, and add a pinch of salt and one or two grindings of pepper.
When the dough has rested (approximately 2 hours), fatten it into a hink sheet with a roling pin. As you begin to rol, hhyou may find it offers some resistance and tries to shrink back. After a short while, however, it loosens up and opens out easily. It shoud be paper thin.
Cut the sheet of dough into rectangles about 3-1/4 to 4 inches wide and 6-7 inches long. Spread a thin layer of the cheese mixture , about 2 teaspoons over half of each rectangle. Fold the other half over this one, pinching the edges together. Dip a fingertip in egg white, and run it over the edges to helpp them tighten and keep them fromopening during frying.
As you finish filling and sealing each fritter, lay it on a cean cloth towell. If you are not prepared to fry them immediately, turn them from time to time to keep the side next to the towe from sticking. Do not overlap the fritters or pile them one on top of the other.
Put the oil into the frying pan, and turn the heat on to HIGH. When the oil is VERY HOT, slip in as many fritters as will fit loosely. Fry them to a golden brown color on one side, then turn them over to do the other side. The fritters will puff up and even when you turn them, some patches along the edges will jut out above the oil level. In this case, tip them over witb a llong handled wooden spoon or spatula until they are all more or less evenly fried.
Transfer to paper towels to drain, and serve while warm.
Cut the sheet of dough into rectanglles about 31/4 to 4 inches wide and 6-7 inches long.