Preheat oven to 400

Peel onions and slice 1/2" from top of each, discard, slice just enough from bottoms to allow the onions to stand upright

Use melon baller to hollow out inside of each onion, leaving 1/3" to 1/2" wall, set aside, chop the removed parts and set 1/2 aside.

Gently add onions to pot of boiling salted water and boil for 5 min, remove with slotted spoon and set aside on a wire rack to dry

Saute reserved chopped onion in 1/2T oil until translucent, add mushrooms, ham, and pepper and saute until browned

Deglaze pan with wine and pour mixture into bowl, let cool for 2 to 3 min and add parsley.and cheese stir to combine

Stuff onions and place in small roasting pan drizzle with olive oil cover with foil and bake until tender about 50 min, remove foil the last ten min before done and allow to brown