Place the butter in a bowl and whip with a whisk until light and creamy, stir in the chopped parsley, garlic, salt and pepper. Set aside.
Tear the bread into small pieces and place onto a baking tray, drizzle with the olive oil and season with salt and pepper. Place into the oven and toast until light golden in colour approximately 4-5 minutes. Remove and reserve aside.
Place the mushrooms in an oven proof dish big enough to allow the mushrooms to slightly overlap each other. Place a good blob of garlic butter on each of the mushrooms and season with a little salt and pepper.
Lay the slices of jamon loosely on top of the mushrooms and sprinkle generously with the breadcrumbs.
Grate or crumble the cheese on top and place into the oven for 10 minutes until the mushrooms are cooked and the bread crumbs are bubbly and golden brown.