Tortellini Alfredo

2 pkgs. (9 oz each) refrigerated cheese tortellini
1/2 cup chopped onion
1/3 cup butter or margarine
1 1/2 cups frozen peas, thawed
1 cup thinly sliced fresh mushrooms
1 cup cubed, fully cooked ham
1 3/4 cups whipping cream
1/4 tsp. coarsely ground pepper
3/4 cup grated Parmesan cheese
shredded Parmesan cheese, optional

Cook tortellini according to package directions. Meanwhile, in a skillet, saute the onion in butter until tender. Add the peas, mushrooms and ham; cook until mushrooms are tender. Stir in cream and pepper; heat through. Stir in grated Parmesan cheese until melted.
Drain tortellini and place in a serving dish; add the sauce and toss to coat. Sprinkle with shredded Parmesan cheese if desired.