Preheat oven to 350 F.
In a medium saucepan, warm cream, crushed garlic, a generous amount of salt and pepper, and dillweed, over very low heat until hot, stirring often. Do not let the cream mixture boil or it will separate. Remove from heat and set aside.
While the the cream sauce is cooking, heat half the butter in a large skillet and brown the sausage until golden brown. Remove sausage from the skillet using a slotted spoon. Using the same skillet, heat the remaining butter. Add onions. Cook, stirring occasionally until the onions are caramelized and lightly brown. Divide the onions and sausage and set aside.
Spray a 9 x 13 glass casserole dish with non-stick cooking spray. Layer 24 perogies on the bottom. Spread half of the onion and sausage over top of the perogy layer. Layer another 24 perogies on top and repeat with the remaining onions and sausage. Gently pour the cream sauce over top of the perogies.
Bake at 350 F for 60 minutes, uncovered, until the sauce is bubbling and golden brown on top. Remove from the oven and serve.
TIP: To save time, perogies can be placed in the casserole dish frozen, but will have a firmer texture than if parboiled.