This chunky mixture is essentially a sauté of eggplant, zucchini, tomatoes, bell peppers, onions, and garlic. I added ground tomatoes, making it a tomato sauce with lots of vegetables (a pasta primavera of sorts). It turned out to be delicious. I love recipes like this: it was quick, my apartment smelled like Little Italy, and I ate a boat load of veggies. I would say that any mix of vegetables that you have on hand would work well. Adding that spoonful of mascarpone cheese to the pan just before serving gave this ratatouille creamy depth and richness.