1 egg
1/4 c. salad oil
3/4 c. water
1 tsp. distilled white vinegar
2 3/4 c. all-purpose flour

Place all the ingredients in the bowl of a heavy electric mixer, such as a Kitchen Aid. Mix with the dough hook until the dough is very smooth. Cover and allow the dough to rest for 15 minutes. Divide the dough into 2 pieces. Roll out 1 piece of the dough into a very thin rectangle. Place a rope of the filling, about 3/4 inch in diameter, 1 inch away from the long edge of the dough. Fold the long edge of the dough over to enclose the filling; press to seal. Cut the filled roll away from the rest of the dough. Using the narrow edge of the handle of a table knife, press and cut the roll into individual Knishes, 2 inches long. Place the Knishes on oiled baking sheets. Repeat with the remaining dough and filling. Bake at 425 degrees, uncovered, until lightly browned, about 20 minutes.

POTATO ONION FILLING:

4 lg. yellow onions, peeled and finely chopped
1/4 c. butter
1/4 c. rendered chicken fat
3 1/2 lbs. potatoes, peeled
Salt and freshly ground black pepper to taste

Saute the onions in the butter and chicken fat until golden. Boil the potatoes; drain and mash. Add the onions along with any oil that remains in the pan. Season with the salt and pepper.

CHEESE FILLING:

2 lg. yellow onions, peeled and chopped
4 tbsp. butter
12 oz. cream cheese, cut up
2 1/4 lbs. dry curd cottage cheese or Farmer cheese

Saute the onions in the butter until golden. Mix the onions in with the remaining ingredients, including any butter left in the pan; cover and chill.