Bring a pot of water to a boil. Cook green beans for 3-4 minutes or until tender but crisp.
Drain beans in a colander, then place in an ice water bath. Drain again in a colander. Pat dry, and set aside.
In a large skillet, cook the chopped bacon over medium heat until it's crispy. Remove from the skillet to a paper towel lined plate. Carefully pour all but 2 tablespoons of the bacon grease in a small bowl.
Add the chopped onion to the skillet. Cook until they are soft and translucent, about 5 minutes.
Stir butter into the onions. Add the drained green beans, and toss with the onions. Season with salt and black pepper to taste. Sauté for 1 minute.
Transfer to a serving dish and garnish with the cooked bacon.
