Preheat oven to 400F and cut off the top third of the whole head of garlic to expose cloves. Drizzle bulb with EVOO, wrap tightly in foil and roast to tender, 40-45 minutes.
Once garlic has been roasted, cover potatoes with water and bring to a boil. Salt water and cook to tender, 12-15 minutes. Drain potatoes and return to warm pot, add all of the roasted garlic and a half a cup of milk or half-n-half to start. Add butter and mash, stir in beaten egg, half of cheese, pepper and nutmeg, and mash to desired consistency. Add a splash more liquid if necessary, cover and reserve.
Meanwhile, heat 1 tablespoon EVOO, a turn of the pan, over medium-high heat. When oil smokes, pat beef dry and add beef to brown. Once very brown, season with salt, pepper and rosemary. Add sausage and brown, add onions, peppers and chopped or sliced garlic cloves. Stir in tomato paste, cook 1 minute, then stir in wine and reduce by half. Add stock and simmer to combine flavors and soften peppers and onions.
Transfer meat to a casserole dish, top with potatoes and remaining cheese. Bake 20-25 minutes until potatoes are brown and crispy at edges, garnish with parsley and serve.