Heat the olive oil in a large skillet over medium-high heat. Add the chicken and cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.
Add the sliced mushrooms to the same skillet and cook until they release their moisture and start to brown, about 5 minutes.
Add the minced garlic to the skillet and cook for 1 minute until fragrant.
Pour in the chicken broth and scrape up any browned bits from the bottom of the skillet. Let it simmer for 2 minutes.
Reduce the heat to medium-low. Stir in the heavy cream and bring the mixture to a gentle simmer. Do not boil.
Stir in the grated Parmesan cheese until the sauce is smooth and thickened. Taste and adjust salt and pepper if needed.
Return the cooked chicken to the skillet. Stir to coat the chicken in the sauce. Heat through for 1-2 minutes.
Remove from heat. Garnish with fresh parsley before serving.
Notes
If you prefer a thicker sauce, simmer the cream mixture for an extra minute or two before adding the cheese.
You can add 4 ounces of cooked fettuccine pasta to the skillet at the end if you want a full pasta meal.
Use fresh mushrooms for the best flavor and texture.