Peel the eggplant if the skin is thick or the eggplant is less than perfectly firm; cut it into 1/2-inch cubes and salt them if the eggplant are large and time allows. Put the olive oil and all but 1 teaspoon of the garlic in a large, deep skillet, preferably nonstick or cast iron, over medium heat. Two minutes later, add the eggplant. Stir and toss almost constantly until the eggplant begins to release some of the oil it has absorbed, after 5 or 10 minutes. 2. Add the reserved tomato and bean sauce along with olives, capers and crushed red pepper to a small skillet with a lid or Dutch oven, over medium-high heat. Cook until eggplant is tender, 20 to 30 minutes.3. Lay the fish in the sauce and add water, if needed, so that the sauce comes just up to the top of the fish, not over it. Bring to a boil, then cover and remove from the heat. The fish will be done in about 10 minutes (a thin-bladed knife inserted between bone and flesh should reveal little or no translucence; if not, return the pan to a simmer and cook for another minute or two more). Remove the fish with a slotted spoon and serve, topped with vegetables and a little of the broth, garnished with the herb.