Pound chicken to 1/2 inch thick. Season with salt and pepper, coat with flour. Heat olive oil in skillet, cook chicken until golden brown, about 4 to 5 minutes per side; transfer to a plate.
STEP 2
Chop shallot and garlic while chicken cooks.
STEP 3
In the same skillet, heat more oil. Cook sliced mushrooms on medium-high, tossing until golden brown, about 5 minutes. Add shallot and garlic, season, and cook for 2 minutes.
STEP 4
Add chicken broth and Marsala wine to skillet with chicken. Simmer until liquid is reduced by half, about 4 minutes. Sprinkle with parsley and serve.