Method
Purée olives, mustard, and olive oil. For each sandwich, grill two slices of sourdough bread and spread one side of each slice with 2 oz of olive-mustard purée. Layer 2 oz of eggplant, 2 oz of peppers, 1/2 oz of onion, and 2 oz of zucchini between two slices of bread and cut in half.
Variation: Add tomato and fresh basil.