Much easier to make than individual perogies. Can make a day ahead and bake just before serving. Will keep hot in a warming tray for parties. If you want to make individual perogies, you can use round wonton wrappers, fill with a small amount of potato filling, fold, seal and boil until they float. Serve with the extra butter/onion mixture.
Peel potatoes. Cut into large chunks. Boil in salted water until fork tender. Drain well.
While potatoes are boiling, saute the chopped onion in butter until tender.
Mash potatoes in large mixing bowl being sure not to leave lumps. DO NOT ADD ANY MILK! Add half of the butter/onion mixture. Add shredded cheese and farmers cheese. Mix well. Salt and pepper to taste.
Put half of remaining butter/onion mix in bottom of a greased lasagna dish. Cover bottom of dish with a layer of lasagna noodles. Add all of potato mixture. (Note, if pan doesn't hold all of the potato mixture you can bake it in a separate casserole dish). Put another layer of noodles on top. Spread remaining butter/onion mixture over top. Cover with foil. (May make to this point and refrigerate. If so allow extra baking time). Bake at 350F for 1 (one) hour or until heated through. Remove foil and bake 5 minutes longer to allow slight browning of the top. Let sit 15 minutes before serving. Serve with plenty of sour cream on the side.