Pancakes: Beat 3 eggs and combine matzo cake meal, potato starch and salt together in a large bowl. Thin the batter with milk until very runny. Grease an 8-inch skillet.
Pour the batter and roll around the skillet until the batter covers the skillet (it will be a very thin coat). Fry the crepes until set or slightly brown. Turn out onto clean towel and cool.
Filling: Mix the farmer cheese, sour cream, 1 egg, salt and cinnamon together. Put a tablespoon of filling in center of each crepe and fold to cover the filling.
Crepes can be fried in butter or baked in the oven. Serve the finished blintzes with sour cream or jelly.