Boil the potatoes until well done, drain and mash with butter. Set aside. In a large skillet over medium heat cook the onions and bacon together. Reserve 1/2 cup of mixture for spooning over the cooked perogies. Add the remaining bacon and onions to the potatoes. Stir the cheese into the potato mixture. Mix well. Chill until very cold. Mix flour and salt in large bowl. Make a well in the middle. Pour water and oil into the well. Mix together. Add more flour, 1/2 cup at a time until dough is firm. Knead dough until mixture does not stick to hands. Cover tightly and let stand for 1/2 hour in a warm place. On a lightly floured surface, roll out dough to 1/4-inch thickness and cut in 2-inch diameter circles. Add 1 teaspoon filling, fold over 1 half of circle and press the edges together to seal. Bring a large pot of water to a boil, add 1 tablespoon oil, then add perogies. Stir occasionally to perogies won't stick to the bottom. When perogies rise to the top, add 1 cup cold water to stop the cooking. Remove the perogies with a slotted spoon. Perogies will cook in 3 to 4 minutes. Serve topped with reserved onion-bacon mixture.