A flavorful shallot-y vinaigrette and gently crisp-tender steamed green beans combine into more than the sum of their parts in this popular summer (or fall) salad. It ages well (it is marinated, after all) and stands up very well to a stint on a buffet table, so it's perfect for picnics, potlucks, holiday tables, or anytime people may be eating at unpredictable times. Go ahead and double or triple it if you're expecting a crowd.
- Trim the green beans as needed. Many varieties of green beans sold today just need their vine-end snapped or cut off; traditional "string bean" varieties are entirely more delicious when you bother to snap off the vine-end and use it to pull off the string running down the side of the bean. Set the trim green beans aside. Prepare a large bowl of ice water and set it aside.
- If you're using a steamer basket, fill a pot it fits in with an inch of water and bring it to a boil; or bring a 1/2-inch of water to a boil in a frying pan; or put the beans in a microwave-safe container with 2 tablespoons of water.
- Put the beans in a steamer basket over the boiling water or in the frying pan with the water, cover, and cook until as tender as you like, 3 minutes fro crisp-tender and closer to 6 minutes for fully cooked beans; or microwave in 1-minute intervals until desired temperature is reached.
- Once the beans are steamed as you like them, immediately plunge them in the ice water. Swish the beans around until they're completely cool. Dry them thoroughly. I like to lay them in a single layer on a clean kitchen towel or paper towels and pat them dry. Put the dried green beans in a shallow dish.
- Peel and mince the shallot or onion, vinegar, and salt in a small bowl. Whisk the sugar, mustard, and oil into the shallot mixture. Pour the dressing over the green beans, toss so all the green beans are coated with the dressing, cover the container, and chill at least 1 hour and up to overnight. (Note that green beans kept over night will loose some of their brilliant green color, but will be just as, if not more, delicious.)