Adapted from www.realsimple.com
Salt and black pepper
1 lb green beans, trimmed
3-6 slices bacon
½ c. onion, sliced
1 T. cider vinegar
1 T. whole-grain mustard
1 T. olive oil
Bring a large pot of water to a boil and add 1 t. salt. Add the green beans and cook until just tender, 4 to 5 minutes. Drain and run under cold water to cool; transfer to a serving bowl.
Meanwhile, in a medium skillet, cook the bacon over medium heat until crisp, 6 to 8 minutes; transfer to a paper towel-lined plate. Let cool, then break into pieces.
Discard all but 1 tablespoon of the bacon drippings from the skillet and return to medium heat. Add the onions and cook, stirring, for 1 minute. Stir in the vinegar, mustard, oil,1/4 teaspoon salt, and1/8 teaspoon pepper. Add to the green beans, along with the bacon, and toss to combine.