SLICE top off bread, 1/2 inch (1.2 cm) down; reserve. Hollow out bread, leaving 1/2 inch (1.2 cm) crust.

SAUTE mushrooms in butter until tender.

LAYER inside bread half the cheeses, ham, mushrooms, tomatoes and onions; repeat layers.

REPLACE top and wrap in foil.

BAKE at 350°F (180°C) for 45 minutes or until cheese is melted. Cool 10 minutes and cut into wedges to serve.