There are many recipes for this and a short cut is to get a jar of the ready made sauce.
Chop the mushrooms and spinach. Put the water to boil for the pasta.
After you sauté the mushrooms in EVOO +/- butter, let them lose water a bit, add salt and grated garlic, try to get them a little crispy. Once done, remove from pan and add spinach. Season the same way and allow water to cook off.
Meanwhile, cook the fettuccine noodles to your liking and drain, keeping some of the pasta water.
Then build the sauce. Melt some butter, add some EVOO to keep from burning, add garlic if you like, then add cream.
Once it boils, be careful not to have it so high that it sticks to the bottom and burns. I stir in the grated cheese slowly so it melts. I also put the cream cheese here too with pepper, cayennne, and a tiny bit of salt.
Taste it as you go along to see if more salt is needed.
Once the thickness that you want is achieved, it should coat the back of a spoon, then start adding ingredients.
Then add chicken, mushrooms, spinach and taste again to see if more salt or heat is needed.
6 small chicken thighs
1 box fettuccine
2 cups chopped mushrooms
2 cups chopped fresh spinach (or 1 cup frozen spinach)
1/2 stick of butter (1 whole stick would work too)
3-5 tablespoons of garlic paste (or 6 garlic cloves grated)
2 cups half and half (heavy cream is more typical, but I was trying to make it a bit lighter)
1 cup pasta water (to thin out sauce as needed)
1 cup finely grated parmigiana
4 oz lite cream cheese ( don’t think you need this if you use heavy cream)
Sea salt, pepper, cayenne pepper