Slice the meat thin and pound it with a wooden mallet. Place in a baking pan. Marinate with the carrot, celery and onion. Add the garlic and bay leaf to the bowl with the meat and cover with the wine. Marinate in a cool place for a couple of hours.
Drain the slices of meat, pat dry and cover each with a slice of pancetta. Roll each slice, with the pancetta on the inside, and tie the involtini with string or keep in place with a toothpick. Drain the vegetables, put them in a saucepan and sauté with half the butter and two teaspoons of oil. When tender (but not browned) add the involtini and brown quickly.
Reduce the wine by half its volume in a separate saucepan. Pour it over the involtini, add salt and pepper, cover and cook over very low heat for 30 mins. When the involtini are ready, remove the string or the toothpick and place them in a warm platter. Drain the cooking liquid, and reduce for another few minutes. Add the remaining butter without allowing the sauce to boil. Pour the sauce over the involtini and serve hot with polenta or mashed potatoes.
