In a large pot of salted water cook the green beans about 5-6 minutes, only until just tender but still with some "bite".
In a saucepan, heat the olive oil on medium heat and fry the onion for 5 minutes, until softened. Add the garlic and cook another minute. DO NOT burn the garlic!
Drain the green beans well and add to the saucepan with the garlic. Cook, stirring constantly for 2-3 minutes. Stir in the crumbled bacon. NOTE: If using Serrano or Parma ham, add it at the same time with the garlic.