Preheat oven to 400 degrees F. In a large pan over medium heat, add oil and onion. Saute onion until soft, but not brown. Add ground lamb to pan and continue cooking for 12 minutes or until cooked through and browned. Season with salt and pepper. In a separate, small pan over medium low heat add 2 tablespoons butter and corn kernels. Cook for 3 minutes and season with salt and pepper.

Cut butternut squash in half and place skin side down on a baking pan. Roast the butternut squash for approximately 40 minutes at 400 degrees F or until very soft. When finished, cool slightly and scoop out meat from the skin with a large spoon. In a bowl, mash the butternut squash and add 2 tablespoons of butter and 1 tablespoon brown sugar. Season with salt and pepper, place aside.

Peel potatoes and place in a large pot. Add enough cold water to cover potatoes by 1 inch. Put pot, covered over high heat and bring to a boil until a thin bladed knife or toothpick can be inserted easily, about 15 minutes. Drain and mash potatoes with 4 tablespoons of butter and 1/4 sour cream. Season with salt and pepper and put aside.

Cut acorn squash in half the long way and remove seeds with a spoon. Cut a small piece off the back of the squash so it will lay flat on a baking sheet. Roast cut side up for 40 minutes at 400 degrees F until soft.

To assemble, place equal amounts of corn in each acorn squash to form the first layer. To create the second and third layers, place a generous amount of ground lamb and butternut squash on top of the corn. Top with mashed potatoes using either a spoon or pastry bag and pipe. Place filled squash on baking sheet pan and roast in the oven for 20 minutes at 400 degrees F or until potatoes are browned. Serve hot with brown gravy.