Finely dice the onion, ham, capsicum, pineapple and mushroom stalks.
Saute in a saucepan with the garlic until the vegetables are soft then stir in the pizza sauce and half the cheese. Continue to heat until the cheese is melted.
Add the stuffing in a heaped fashion to each mushroom then place on a baking tray. Sprinkle each mushroom with the remaining cheese and some basil. Place under a medium grill and cook until the cheese melts and starts to brown, about 5 minutes.