Fry the chicken fillets in olive oil and butter with the garlic bulb cut into individual cloves for 10 minutes. Deglaze with balsamic vinegar and let simmer for 2 minutes. Add the marsala and stock, cover and simmer gently for 20 minutes, turning once.
Sieve the sauce, keep the meat warm. Press the garlic cloves through the sieve. Stir the mascarpone into the sauce and let everything simmer a little. Serve with the meat.