Fry bacon. Cut into small pieces. Discard bacon drippings. Melt butter in pan, add chopped onion, bacon and peas. Saute 10 minutes on medium heat. Add heavy cream, milk, grated cheese, parsley, salt and pepper. Simmer 20 minutes on low heat. Shut off heat. Wait 5 minutes. Stir in egg yolks. Stir sauce into cooked fettuccine and serve.