1 3/4 cups reduced-sodium chicken broth (14 fl oz)
2 tablespoons finely chopped shallot
5 tablespoons unsalted butter
10 oz mushrooms, trimmed and thinly sliced
1 1/2 teaspoons finely chopped fresh sage
1/4 teaspoon salt
1/8 teaspoon black pepper
1 cup all-purpose flour
4 skinless boneless chicken breast halves (2 lb total)
2 tablespoons extra-virgin olive oil
1/2 cup plus 2 tablespoons dry Marsala wine
2/3 cup heavy cream
1 teaspoon fresh lemon juice