Begin by boiling your pasta so it finishes around the same time as the chicken. Cook according to package instructions and set aside.
Slice each chicken breast in half to create thinner cutlets. If needed, gently pound any thick parts so everything cooks evenly. Season both sides with salt and pepper.
Heat olive oil in a large skillet. Add the chicken and cook for about 5–6 minutes per side, until fully cooked and golden. Remove from the skillet and cover loosely to keep warm.
In the same skillet, add butter. Once melted, stir in sliced mushrooms and minced garlic. Cook for about 4 minutes until the mushrooms soften and start to brown.
Sprinkle the flour over the mushrooms and mix well. Slowly pour in the chicken broth, scraping up the browned bits at the bottom. Add the Marsala wine and let the sauce simmer until reduced by nearly half. Stir in the heavy cream for a silky, rich finish.
Return the cooked chicken to the skillet, spooning the sauce over it. Serve warm over fettuccine so the pasta absorbs all that delicious creaminess.