Cook pasta according to directions and while the pasta is cooking start heating your skillet.
Heat oil over medium high in a large skillet. Remove the sausage from the casing and crumble into the skillet. Brown sausage while breaking into small pieces add the mushrooms and saute for 5-7 minutes. Add half of the chicken stock and cover. Continue to cook over medium heat for ten minutes. Add in the peas and cook until the peas are heated through - about 5 minutes.
Mix the cornstarch into the remaining chicken stock and add to the skillet along with the butter. Stir until well mixed and thickened. Toss the drained pasta in the skillet with the sausage mixture and top with the fresh parsley.