Dice the red onions into small pieces. Slice the mushrooms and set aside. In a saute pan turn the pan to medium-high heat. Add the onions to the pan and begin to saute. Add the ground beef and continue to saute with the onions until the beef has been browned. Sprinkle the corn starch over the beef and continue to mix until the cornstarch is combined into the meat. Add the black pepper, dash cayenne pepper, garlic powder, salt and worchestershire sauce. Add the mushrooms to the beef and continue to saute until they are tender. Add the evaporated milk and sour cream and stir until combined. The mixture will start to thicken quickly, so continue to stir so the mixture is smooth.
While the mixture is cooking, bring a large pot of water to a boil and boil the egg noodles (or you can serve over cooked rice). Once the noodles are tender, drain and place in a bowl.
Once the mixture is smooth and to your desired thickness, serve over the cooked noodles. Garnish with the chopped parsley.