Preheat oven to 400 F. Dredge chicken in flour mixed with salt and pepper. Add oil to a hot pan (if there is smoke it is too hot). Sear chicken on both sides. Place into the oven.

In the same pan that the chicken was seared add mushrooms. When the mushrooms are almost done add garlic and shallots, garlic will burn easily so watch closely. When the garlic starts to darken add the marsala wine. 

Cook until the wine has reduced by half.

Add chicken stock. Cook until reduced by half.

Add half-n-half and cook until slightly thickened (it won't thicken like heavy cream will, so you are aware) stirring gently to keep anything from sticking to the bottom.

Salt and pepper to taste. When the chicken is cooked all the way place it on the cooked pasta. Pour the sauce over the top.