1. Preheat broiler to high.
2. Heat olive oil in a saucepan over medium-high heat. Add onion; sauté 3 minutes. Stir in garlic; cook for 1 minute. Add basil and tomatoes; bring to a boil. Stir in cheese until melted. Place mixture in blender, and blend until smooth. Return to pan; stir in milk, salt, and pepper. Return to medium-high; cook 2 minutes.
3. Place bread on baking sheet; lightly coat with spray. Broil 1 minute. Rub garlic over toasted side; turn bread over. Top with Asiago; broil 1 minute.