Mince garlic and chop onion. Slice mushrooms.
4 garlic cloves, ½ medium yellow onion, 6 oz white mushrooms
Mix milk and cornstarch in a cup. Set aside.
½ cup whole milk, 2 teaspoons cornstarch
Preheat oven to 350℉ and get your 13″ x 9″ baking dish ready.
Place flour in a shallow dish.
¼ cup all-purpose flour
Slice each chicken breast in half lengthwise. Season with salt and pepper and dredge each piece in flour.
2 large chicken breasts, ½ teaspoon salt, ¼ teaspoon black pepper
In a large skillet, melt butter and heat up the oil. Brown chicken on both sides. Remove from the skillet onto a plate and set aside.
1 tablespoon olive oil, 1 tablespoon unsalted butter
Add onions and garlic to skillet and saute until almost translucent. If needed, add more butter to the skillet.
Add mushrooms and thyme and saute for 4 to 5 minutes, stirring often.
½ teaspoon dried thyme
Add broth and deglaze the pan (using a wooden spoon, scrape the bottom of the pan so all cooked-on bits come off; this is flavor).
¾ cup chicken broth
Give the milk and cornstarch mixture a stir and add to the skillet. Simmer the sauce until thickened.
Arrange cooked chicken in your baking dish.
Pour the mushroom sauce over the chicken. Using kitchen tongs, move the chicken around so the sauce has a chance to get onto the bottom of the dish too.
Place slices of cheese on top of the chicken and sauce.
6 to 8 slices of Muenster cheese
Bake the dish for 10 to 15 minutes OR until the cheese is melted and the sauce is bubbling around the edges.