Chicken Marsala

4 Tbsp. butter
4 skinless, boneless chicken breast halves, pounded to 1/4-inch thickness
4 shallots, finely chopped (or about a 1/4 cup finely chopped onion)
1/2 pound mushrooms, sliced
1/4 cup dry Marsala
1/2 cup heavy cream
1 teaspoon lemon juice
Salt and freshly gound pepper

In a large frying pan, melt 2 Tbsp of the butter over medium heat. Add chicken and saute, turning once, until lightly browned, about 2 minutes on each side. Remove and set aside. Melt remaining butter in pan. Ad shallots and mushrooms. Cook until mushrooms are lightly browned, 3 to 5 minutes. Add Marsala and bring to a boil, scraping up any browned bits from bottom of pan. Add cream and lemon juice
and return to a boil. Season with salt and pepper to taste. Return chicken to pan and cook, turning in sauce, for about 3 minutes to reheat and finish cooking.