Creamy white Aztec and black runner beans are mixed with crisp green and yellow Romano beans in this substantial salad.
Rinse heirloom beans. Place in a large bowl of water, and let soak 8 hours or overnight. Drain.
Bring a large pot of water to a boil. Add heirloom beans, carrots, celery, halved onion, garlic, bay leaf, sprigs of thyme and rosemary, sage, fennel seeds, red-pepper flakes, and 1 tablespoon olive oil. Cover; return to a boil. Reduce heat, and simmer, with lid slightly ajar, until beans are soft, 50 to 60 minutes. Add 1 teaspoon salt; stir well, then let beans cool in cooking liquid. Beans can be refrigerated overnight at this point.
Cook each type of fresh bean separately in boiling salted water until just tender but still firm, about 2 minutes. Remove beans from water with a slotted spoon, and plunge into ice water to stop the cooking. Repeat until all fresh beans have been cooked.
In a small bowl, combine both vinegars; add shallots and garlic. Gradually whisk in 4 1/2 tablespoons olive oil until mixture thickens. Whisk in chopped thyme, rosemary, parsley, and salt and pepper to taste.
Drain heirloom beans, and discard the vegetables and herbs. Combine all beans in a serving bowl. Gently mix in vinaigrette; let stand at room temperature for 30 minutes.
Lightly brush onions with remaining tablespoon olive oil. Cook on a medium-hot grill for 5 minutes or under the broiler for 8 minutes on each side, or until browned. Arrange grilled onions over beans, and serve.
The varieties of heirloom beans used here have a meaty texture and rich flavor that work well in this salad. But if you cannot find them at your local farmer's market, you can substitute dried cannellini or gigande beans instead.