4 tablespoons extra-virgin olive oil, divided
1 clove garlic, peeled and halved
4 cups 1/2-inch crusty multigrain bread cubes, preferably day-old
1 pound coarsely chopped peeled cooked shrimp (see Note)
4 large ripe but firm tomatoes, coarsely chopped
2 large green, red and/or yellow bell peppers, diced
3/4 cup chopped fresh parsley
1/4 cup chopped fresh chives
1/4 cup sliced pitted Kalamata olives, plus 1/4 cup olive brine
3 tablespoons red-wine vinegar
1 1/2 teaspoons chopped fresh thyme or 3/4 teaspoon dried
Freshly ground pepper to taste
4 cups mixed salad greens