lot of great soups start the same way: onion, carrot, and celery, cooked slowly in a little fat before any liquid goes in. Italian cooks call it soffritto. French cooks call it mirepoix. In Louisiana, with bell pepper instead of carrot, it's the holy trinity. Gentle heat softens the vegetables and brings out their sweetness, and the fat carries that flavor through the whole pot. Tossed straight into broth, they taste boiled. Cooked slowly first, they taste sweet and deep. The quiet part at the start is where the soup gets its flavor.