Heat butter and olive oil in a medium saute pan. Add onions and sugar and cook slowly until soft and caramelized. Heat olive oil in a large saute pan over high heat. Add the mushrooms and saute until golden brown and cooked down. Season with salt and pepper to taste. Preheat grill. Flatten the dough, brush liberally with olive oil and throw on the grill. Grill on one side until golden brown, turn over spread with the mozzarella, onions and mushrooms and blue cheese.