1. Defrost pizza dough and spread thinly. Smear the garlic over it evenly.
2. Heat one tablespoon oil in a large pan. Add diced onion and brown sugar and cook until browned, about 15 minutes.
3. Clean and thinly slice the Portobello mushrooms. Toss with another tablespoon of oil in a bowl and sprinkle with Montreal steak spice. Set aside.
4. Sprinkle cheese over the dough. Spread the mushrooms and onions evenly over the top. Drizzle barbecue sauce over the pizza and bake for 15 minutes, or until ready. Add the arugula and serve immediately.