2 bulbs garlic, ends cut to expose cloves, divided
Olive oil, for drizzling plus about 2 tablespoons
Pound chunk guanciale or pancetta, diced inch
1 1/2 pounds coarse ground sirloin
Salt and pepper
2 carrots, chopped
2 ribs celery from heart, chopped
1 onion, chopped
1 bay leaf
Herb bundle of parsley, sage and rosemary, a few sprigs of each
2 tablespoons tomato paste
1 cup dry red or white wine
2 cups beef or veal stock
1 to 2 cups whole milk, divided
A chunk of Parmigiano-Reggiano cheese rind, optional
2 pounds Russet potatoes, 5 large, peeled and cubed
1 1/2 cups grated Parmigiano-Reggiano, divided
Freshly grated nutmeg
2 egg yolks
Chopped parsley, about 2 tablespoons
Preheat oven to 425° F. Drizzle exposed cloves of garlic with olive oil, season with salt and pepper and wrap in foil pouch. Roast about 40 minutes until very soft and tender, caramel in color. Cool to handle.
For filling, heat olive oil, 2 turns of the pan, in Dutch oven or heavy pot over medium high heat, add guanciale or pancetta and lightly brown, 2 minutes, add beef and caramelize, browning meat to develop sugars, add salt and pepper, carrots, celery, onions and 1 bulb of roasted garlic, squished from skins, stir well to incorporate garlic, add bay and herb bundle and partially cover, cook 10-12 minutes to soften, stirring occasionally, over medium heat. Stir in tomato paste until fragrant, 1-2 minutes, add wine, stock, 1 cup milk, bring to bubble, reduce heat and simmer gently.
Meanwhile, cover potatoes with water in another pot, bring to rolling boil, salt water and cook to tender, drain, pass potatoes through ricer. Add warm milk, roasted garlic, 1 cup grated cheese, salt, pepper, nutmeg, combine and taste to adjust seasoning then mix in egg yolks.
Preheat broiler and place rack in center of oven.
Transfer beef filling to casserole or individual bowls. Pipe or spread potatoes over top of beef and sprinkle with remaining cheese, broil to brown and serve. Garnish with parsley.