Rub cut side of garlic on side of salad bowl; discard garlic. Trim ends from endive, and remove any wilted or discolored outer leaves; separate leaves. Add endive leaves, lettuces, and onion to bowl; toss gently.
Combine the next 5 ingredients in a small bowl, and stir with a wire whisk until well blended. Pour over salad, and toss gently.