Cook broccoli to package directions.
In large saucepan, saute onion in 3 Tbs butter until tender.
Sprinkle flour over and stir till blended.
Gradually add milk, bring to boil.
Cook and stir for 2 minutes or until thickened.
Reduce heat, stir in cheese until melted.
Drain broccoli, add ham and 1 cup stuffing mix, stir into cheese sauce.
Transfer to 2 qt baking dish.
Melt remaining butter and toss with remaining stuffing mix.
Sprinkle around edge of casserole.
Bake, uncovered, at 350 for 25-30 minutes or until golden brown.