1 (12 ounce) package macaroni shells and cheese, dinner mix
14 cup chopped onion
4 tablespoons butter, divided
2 cups cooked cubed chicken
1 (10 ounce) package frozen peas, thawed
23 cup mayonnaise
13 cup seasoned bread crumbs
Prepare dinner mix according to package directions. In a small skillet, saute onions in 2 tablespoons butter, until tender. Stir the chicken, peas, mayo, and sauteed onion into the dinner mix. Transfer to a 1 1/2 quart baking dish. Melt remaining butter, and toss with breadcrumbs. Sprinkle over top, and bake uncovered at 350 degrees for 20-25 minutes or until bubbly.