Wash portabella caps, place upside down on large baking tray, pour dressing and sprinkle garlic over them (does not need to be submerged in marinade). I sort of smear a bit of dressing around the other side of the portabella to coat.
Halve and hollow out peppers, coat with some of the dressing/garlic and place alongside the portabellas. Set the tray aside.
Cook the bacon. Simplest way is to arrange strips in baking tray and broil ~10 mins in oven (Warning: Burns easily).
Slice mozzarella ball into thick pieces.
Place pepper halves on grill for 5-10 mins and then add portabellas (~5-10 mins on each side), then place slices of cheese on portabellas until melted.
Lightly toast rolls/bread/buns, and stack the portabella with melted cheese, bacon, and pepper half inside.