MUCH TO BE SAID about this delicious dinner, beginning with chevre and herbs on crackers, continuing to a fine vegetable soup, then crisp butter lettuces with pears and blue cheese, and finally this amazing tart. Becky made it from Deborah Madison's wonderful Vegetarian Cooking for Everyone, adapting the Jam Bars recipe, she said, and using elderberries for the filling. Rich, deep, complex, earthy, pungent, pointed, utterly substantial. And then a great old Marc de Provence to finish it off. You can't do better.