Preheat the oven to 400 F. Cut the top of the head of garlic off to expose a portion of each clove. Place in foil, with 1 tsp olive oil and a dash of salt & pepper. Bake for 30 minutes, and check every ten minutes after until the cloves are a deep brown but not burnt.
While the garlic is roasting, warm a pan over medium high heat and add olive oil for cooking the chicken (skip this step if you're not cooking chicken).
Make sure the chicken breasts are either sliced thin or beat thin. Season with salt and pepper. Sear the chicken to a deep golden brown and remove from pan.
Turn the heat down to medium, and add the mushrooms to the same pan. You may need to add more olive oil if the mushrooms are sticking. Cook the mushrooms down to half their original size.
Add the butter, and whisk in the flour. Make sure all of the mushrooms are coated with flour. Add the chicken stock, heavy cream, parsley, and squeeze in the garlic cloves (the garlic cloves will slide out of their casing once they are roasted).
At this stage, put on your pasta water.
Continue to whisk & stir the sauce until it thickens slightly. Turn heat to low once the sauce has thickened. Cook pasta to al dente. Right before you add the pasta to the sauce, whisk in the cheese. Add the pasta over low heat and coat completely.
Nestle the chicken into the pan to heat back up & coat in sauce.
Serve with more grated parm, and enjoy!