Mixed Bean with Scallions Salad

Name: Mixed Bean with Scallions Salad
Ingredients: 1 pound dried heirloom beans, such as white Aztec and black runner, picked over; 2 medium carrots, peeled and cut crosswise into 4 pieces each; 2 celery, cut crosswise into 6 pieces each; 1 small onion, peeled and halved; 2 cloves garlic, smashed; 1 dried bay leaf; 3 sprigs fresh thyme, plus 1 1/2 teaspoons chopped leaves; 1 large sprig fresh rosemary, plus 1 1/2 teaspoons chopped leaves; 4 fresh sage leaves; 1 teaspoon fennel seeds; 1 teaspoon crushed red-pepper flakes; 6 1/2 tablespoons extra-virgin olive oil; 1 teaspoon salt, plus more to taste; 2 1/2 pounds mixed fresh beans, such as baby green beans and green and yellow Romano beans, trimmed; 1/4 cup red-wine vinegar; 2 tablespoons sherry vinegar; 1/2 small shallot, minced; 1/2 teaspoon minced garlic; 1 tablespoon finely chopped fresh flat-leaf parsley, leaves; Freshly ground black pepper; 10 to 12 spring onions, peeled and sliced into 1/2-inch rounds