For the dressing: In a jar with a lid, combine the oil, Champagne vinegar, shallots, mustard, garlic and 1/2 teaspoon each salt and pepper. Tightly close the lid and shake so the dressing is well combined.
For the salad: Put the mixed greens and romaine in a large bowl. Add enough dressing so that each leaf is lightly coated when tossed. Sprinkle with additional salt and pepper. Transfer the lettuce to a serving platter or bowl.
Scatter the tomatoes and mozzarella balls over the salad along with the pine nuts and finally the basil leaves. Serve immediately.