Dissolve yeast in water. Add oil, sugar, egg and salt; mix well. Add flour and mix. Cover and let rise for 45 minutes. Knead well and let rise again for 30 minutes. Knead dough and roll to about 1/4-inch thick. Cut into 4 squares.
Brown hamburger and onion until red disappears. Add cabbage and salt and pepper to taste.
Put 2-3 tablespoons filling of cabbage mixture in center of rolled out dough. Bring corners together at top, pinching edges securely; turn upside down and place on cookie sheet. Bake at 350* for 30 minutes.