4 (6 ounce) skinless, boneless chicken breasts
sea salt and ground black pepper to taste
1/4 cup extra-virgin olive oil, divided
3 tablespoons unsalted butter, divided
1 small shallot, finely chopped
6 slices prosciutto, cut into thirds
1 (8 ounce) package cremini mushrooms, stemmed and halved
1/2 cup sweet Marsala wine
1/2 cup chicken stock
1/4 cup chopped flat-leaf parsley
1. Slice chicken breasts in half widthwise using a sharp knife. Cover with plastic wrap; pound with the flat side of a meat mallet to 1/4-inch thickness. Season both sides with salt and pepper.
2. Heat 1 tablespoon olive oil and 2 teaspoons butter in a large skillet over medium heat. Add 3 chicken pieces; cook until golden, about 5 minutes per side. Transfer to a large platter. Cook remaining chicken pieces in batches, adding 1 tablespoon olive oil and 2 teaspoons butter for each batch.
3. Cook and stir shallot and prosciutto in the hot skillet until shallots soften, about 1 minute. Add mushrooms; cook until browned, about 5 minutes. Season with salt and pepper. Pour in Marsala wine; cook until slightly reduced. Pour in chicken stock; simmer until slightly thickened, about 1 minute.
4. Stir 1 tablespoon butter into the skillet. Return chicken to the skillet; simmer until heated through, about 1 minute. Garnish with chopped parsley.