4 pounds green beans (preferably Blue Lake variety), trimmed
1 cup extra-virgin olive oil
1 medium Spanish onion, thinly sliced
4 garlic cloves, smashed and peeled
1 bay leaf
1 dried red chile pepper
4 cups chicken stock or low-sodium chicken broth
1/2 cup aged balsamic vinegar
1 tablespoon kosher salt
2 teaspoons freshly ground black pepper
Bring large pot salted water to boil. Add green beans and boil, uncovered, until slightly tender but still crisp, about 3 to 4 minutes. Drain and set aside.
In large saucepan over moderately high heat, heat 1/2 cup olive oil until hot but not smoking. Add onions, garlic, bay leaf, and chile pepper. Sauté, stirring occasionally, just until soft, about 4 to 5 minutes. Add green beans, chicken stock, vinegar, salt, pepper, and remaining 1/2 cup olive oil. Bring to simmer, then reduce heat to low and simmer, covered, 30 minutes. Strain, remove chile and bay leaf, and serve immediately.