Vibrant Vegetarian Ratatouille

Name: Vibrant Vegetarian Ratatouille
Ingredients: 2 medium eggplant (cut into cubes); 4-5 tablespoons olive oil; 1 large onion (halved and sliced); 2-3 garlic cloves (finely chopped); 1 large red or yellow bell pepper (seeded and cut into thin strips); 4 courgettes (2 small zucchini and 2 small yellow squash, cut into 1/2-inch slices or cubes); 2 cups diced tomatoes; 1 1/2 tablespoons Herbes de Provence; Salt and freshly ground black pepper to taste; Optional: oyster sauce (balsamic vinegar, or grated lemon zest)