Preheat oven to 375 F.
Take 2 bulbs of whole garlic and turn them upside down (root side down) and place in roasting dish. With a sharp knife, slice across the top of the bulb to expose the garlic cloves.
Drizzle olive oil, kosher salt, ground black pepper over exposed garlic, cover dish with a lid or foil and bake for approximately 45 minutes or until tops of garlic turn a deep golden brown.
When done, remove from oven, remove top of dish and let garlic cool for 15 minutes. Then carefully remove garlic from dish and squeeze out the roasted cloves from the skin by putting the root end inside your palm with exposed side of garlic facing out, just like squeezing a half of lemon.
For potato puree: Bake (washed, but unpeeled) potatoes in 375 F oven until fork-tender (approximately 45 minutes, this can be done at same time as roasting the garlic).
Heat cream and butter in saucepot until simmering and hold warm.
When potatoes are done, remove from oven and, using a kitchen towel or wearing clean rubber gloves to protect from the heat, peel the hot potatoes and put the peeled potatoes through a food mill.
Add hot cream mixture to potatoes, add seasoning, add roast garlic puree and mix all together thoroughly. Adjust seasoning as needed.
In a heavy-bottomed stock pot sweat the onions, garlic, shallots, ground lamb and the filet until all are thoroughly golden brown, about 10 minutes.
Add seasonings, vegetables and liquids and simmer for 10 minutes. Transfer entire mixture into casserole dish and top with the garlic-mashed potatoes. Sprinkle entire top with cheese and bread crumbs and bake uncovered in 350 F oven for 30 minutes in order to set entire dish.