01 -
Preheat oven to 375°F with rack in top third. Cut chicken breasts lengthwise into 6 cutlets. Season with salt and pepper, then coat in flour.
02 -
Heat oil and 1 tablespoon butter in a skillet over medium-high heat. Brown chicken in batches, 3-4 minutes per side. Transfer to 9x13 casserole dish.
03 -
In same skillet, add 1 tablespoon butter and cook mushrooms until seared and water evaporates, about 5 minutes. Add to casserole dish.
04 -
Melt remaining butter in skillet. Add flour and garlic, cook 1 minute. Add sherry, then whisk in cream until smooth. Cook until slightly thickened.
05 -
Pour sauce over chicken and mushrooms. Top with cheese slices. Cover with foil and bake 20 minutes. Broil uncovered until cheese browns.