Here's the recipe as found in the cook book. Mom always just used plain cottage cheese as the filling.

Filling:

Press

1 lb. farmer cheese

1 egg
1 tbsp. sugar
1 tbsp. soft butter
pinch salt

Batter:

Beat until light and foamy

2 eggs

1/2 tsp. salt 
1 tsp. sugar
1 c. water
1 tbsp. melted butter
1/4 tsp. baking powder (sifted)
1 c. flour (sifted)

Beat until smooth. Drop this batter, 2 tbsp. at a time, onto small frying pan -- 7", on medium heat. Tip pan so batter spreads thinly over entire pan. Pour off excess. Bake one side until top is dry and starts to blister. Turn out onto board. Fill with 1 tbsp. of filling. Roll and fold on both sides. When ready to serve, brush tops with melted butter. Bake at 400 degrees for 1/2 hour. Serve with sour cream, fresh fruit, etc.