With a very sharp knife, cut the chicken lengthwise into cutlets. First butterfly the chicken open and then continue until you have two pieces for each chicken breast. See photos within the post.
1 pound chicken
In the slow cooker, mix together the Marsala wine, garlic cloves, salt, and pepper.
1 cup Marsala wine, 2 cloves garlic, 1/2 teaspoon kosher salt, dash ground black pepper
Add the chicken to the slow cooker and top with the mushrooms. Cook on high for 1 1/2 hours or on low for 3 hours or until the chicken reaches 165 degrees Fahrenheit registered with an instant read thermometer.
8 ounces sliced mushrooms
Pull the chicken out of the crockpot and set aside. Pull out 1/4 cup of the cooking liquid and whisk in the cornstarch. Whisk that back into the liquid in the slow cooker, mixing well. Place the chicken back on top, cover the slow cooker, and cook on high for 15 to 25 minutes or until the liquid has thickened. You will likely need to mix the liquid once or twice during the 15 minutes to fully thicken the mixture.
1/4 cup corn starch
Serve with cooked fettuccine and enjoy.
cooked fettuccine
Notes
Please note that the nutritional information doesn't include the cooked fettuccine.