Green Beans with Caramelized Onions and Walnuts
- 1 1/2 pounds green beans — trimmed
- 1/2 cup chopped walnuts
- 2 tablespoons extra-virgin olive oil — divided
- 4 cups thinly vertically sliced onion
- 1 teaspoon chopped fresh thyme
- 2 teaspoons white balsamic vinegar
- 1/2 teaspoon kosher salt
- 1/4 teaspoon freshly ground black pepper
