Ham & Mushroom Stuffed Zucchini

4 medium sized zucchini (at least 1/2 lb each) OR 3 large zucchini (3/4 lb each) OR 1 jumbozucchini (2 lbs)

4 Tbsp butter, divided

1 medium onion, chopped (about 1 cup)

10 ozs of fresh mushrooms, sliced

1/2 cup finely chopped ham

2 tsps finely chopped parsley

1/2 tsp worcestershire sauce

Salt, pepper, and cayenne to taste

1/3 cup bread crumbs

1/3 cup grated Gruyere or parmesan cheese