Bring a pot of water to a boil and blanch the green beans for 5 minutes. Immediately drain and dump them into a large bowl of ice water to cool for a couple of minutes. Drain and pat dry.
In a large skillet over medium-high heat, fry the bacon until crispy. Transfer to a plate. Melt the butter in the skillet with the remaining bacon grease and cook the onions until beginning to caramelize, about 7-8 minutes. Add the garlic and cook for another minute. Add the beans along with about 1 teaspoon salt, and a little pepper, and cook for 5-6 minutes. You want them crisp but not crunchy hard. Return the bacon to the skillet and stir to combine. Add salt and pepper to taste. Serve immediately.