Peel and chop the garlic.
In a large frying pan or skillet add the olive oil and heat on medium-high heat.
Add the garlic and saute for thirty seconds.
Add the sliced white button mushrooms in a single layer to the pan.
Allow to saute until golden brown stirring once or twice as need.
Add a little more oil if it becomes necessary as mushrooms soak up oil.
Once the mushrooms are sauteed add the black pepper and the chicken stock.
Heat on high until the chicken stock is boiling.
Measure the cornstarch and cold water into a measuring cup and blend well.
Add the cornstarch slurry to the chicken stock and stir continually.
Reduce heat to simmer. Simmer until the mixture is thickened.
Drain pasta in colander and then return to cooking pot.
Pour the finished sauce over the pasta.
Wash and cut up the fresh flat leaf parsley. Add to the pasta and stir to mix all ingredients well.
Serve pasta while hot with fresh parmesan pieces on top.
Store cooled unused leftovers in the fridge in an airtight container for up to five days.