Slice 600g of chicken breasts horizontally into thin cutlets; pound to ½in / 1cm thick. Measure ¾ teaspoon of kosher salt and ⅝ teaspoon of black pepper. Season the chicken with two-thirds of the salt and most of the pepper.
Dust with ¼ cup of all-purpose flour, shaking off excess. Measure 2 tablespoons of olive oil and 30g of butter. Heat half of each in a skillet over medium-high heat.
Fry the cutlets for 3-4 minutes on one side and 2 minutes on the other, until golden; remove.
Add the remaining oil and butter, 2 shallots, chopped, and 1 garlic clove, minced. Cook for 1 minute. Add 2 cups of sliced mushrooms; cook for 3 minutes.
Add 1 cup of dry Marsala wine and boil until reduced by half. Stir in ½ cup of chicken stock, ½ cup of heavy cream and the remaining seasoning. Simmer for 3-5 minutes, until lightly thickened.
Return the chicken and its juices. Heat until the chicken reaches 165°F / 74°C.
