2poundsboneless skinless chicken breasts - about 3 breasts
1medium shallot or 1/2 small yellow onion - finely chopped
1cupdry Marsala wine - not cooking wine
8ouncessliced cremini mushrooms
1tablespooncornstarch - mixed with 2 tablespoons water to create a slurry
For serving: chopped fresh parsley or basil
For serving: whole wheat pasta - zucchini noodles, or simply a big loaf of crusty bread
Lightly coat a large slow cooker with nonstick spray. Heat 1 tablespoon olive oil in a large skillet over medium high. Season both sides of the chicken with salt and pepper. Once the oil is hot and shimmering, add the chicken in a single layer. Cook on the first side for 3 to 4 minutes, until browned, moving the chicken as little as possible so that it gets a nice sear. Flip and brown on the other side, about 2 additional minutes. It does not need to be cooked all the way through. Transfer the chicken to the slow cooker.
Reduce the skillet heat to medium low. Heat the remaining 2 teaspoons oil. Add the shallot and cook until softened, about 3 minutes. Stir in the garlic.
While the skillet is still warm, pour in the Marsala. Increase the heat to medium and let simmer 2 minutes. Remove from the heat.
Scatter the mushrooms over the top of the chicken. Pour in the Marsala reduction. Cover and let cook on LOW, until the chicken is cooked through and reaches 165 degrees F on an instant read thermometer, about 2 1/2 to 3 hours on low (timing will vary based on your slow cooker model and the size of your chicken breasts). Remove to a plate and cover to keep warm.
In a small bowl, whisk together the cornstarch and water. Pour into the slow cooker. Cover and cook on HIGH for 15 to 20 minutes, until thickened. Return the chicken to the slow cooker and let heat over high for 5 additional minutes to warm through. Serve hot with desired accompaniments, with the sauce spooned over the top and a sprinkle of fresh parsley as desired.
TO STORE: Place leftover chicken in an airtight storage container in the refrigerator for up to 3 days. Store the sauce separately.
TO REHEAT: Gently rewarm chicken in a large skillet on the stovetop over medium-low heat. You can also reheat this dish in the microwave. When I reheat chicken, I like to shred or cut it into smaller pieces first to help it heat evenly. Reheat the sauce gently on the stove.
TO FREEZE: Store chicken Marsala in an airtight freezer-safe storage container in the freezer for up to 3 months, either with or separate from the sauce. Let thaw overnight in the refrigerator before reheating.
Photography note: the photos of this recipe show the sauce cooked down for a far more extended period than is necessary (the cooking time got away from me while photographing!). Your sauce might not look as thick as in the photos, but don't fear; it will still be delicious and is actually closer to how an authentic chicken marsala sauce is meant to be.