In a saucepan, heat up 3 tablespoons olive oil; then add the garlic and farro. Cook the garlic until golden, allowing the farro to get toasted as well. Stir to prevent sticking. Add vegetable broth, a few ladles at a time as you would preparing risotto. Continue stirring and add more broth, a little at a time, as it evaporates. Cook until the farro is soft. In another saucepan, heat up 4 tablespoons olive oil. Add the onion, zucchini, red pepper, eggplant, and then the tomatoes. Add the salt and cook until tender. If the pan is drying out, avoid adding more oil, just add some vegetable broth to help cook the vegetables. Once the vegetables are soft, remove from the heat and add to the farro. Then add the parsley and mint and mix well. Plate the dish, top with walnuts and drizzle with olive oil.