1 pound fresh green beans (thin or thick, whatever kind you can get)
1/2 pound bacon, diced (or more if you wish)
1 large sweet onion, diced
2 T butter
1 T balsamic vinegar (you could substitute apple cider vinegar or wine vinegar)
sea salt & pepper
Cook bacon until almost crisp in a cast iron skillet large enough to hold the whole side dish. Pour out most of the bacon fat (leave enough to lightly coat entire bottom of pan) and reserve it in a mason jar. Add the butter to the pan with the reserved bacon fat, and add the onion. Saute the onion for about 15 minutes or more until it golden brown and caramelized. When the onions are nearly done, add the 2 T of balsamic vinegar and deglaze the pan.
While the onions are cooking, steam the green beans until barely cooked (should still be crisp and not limp – if you’re using very thin green beans you may be able to skip this step and just add the beans to the pan directly). Add the green beans to the cast iron skillet, along with the reserved bacon pieces. Cook all ingredients together for about 5 minutes, until the green beans are completely cooked. Every bean should be lightly coated with the fat (no dry spots). Add more reserved fat if needed.
If the recipe seems dry at any time, add a few teaspoons of the reserved bacon fat.
Taste and season with sea salt and pepper. You may not need any salt at all depending on the amount and saltiness of your bacon.