1. Preheat oven to 400°.
2. Place garlic and onion in a food processor; process until finely chopped. Add 1/4 cup Parmigiano-Reggiano and next 4 ingredients (through pepper); process until almost smooth. Add artichoke hearts; pulse until artichoke hearts are coarsely chopped. Spoon mixture into a 3-cup gratin dish coated with cooking spray; sprinkle evenly with remaining Parmigiano-Reggiano. Bake at 400° for 15 minutes or until thoroughly heated and bubbly. Serve hot with baguette.