In medium saucepan, combine onions, 4 tablespoons vinegar, butter, vegetable oil, thyme, pepper and 1/2 teaspoon salt. Heat over low heat until butter is melted; stirring to coat onions. Place mixture on a baking sheet and roast in a 400° oven for 35-40 minutes, stirring occasionally until onions are browned nicely; remove from oven and set aside. Blanch green beans in large saucepan of boiling water just until tender, about 5 minutes. Drain and rinse with cold water; set aside. In small bowl, whisk together olive oil, mustard, sugar, the remaining 4 tablespoons of the vinegar and the remaining 1/2 teaspoon of salt. In a large bowl, toss the dressing together with the onions and the green beans. Place the mixture in a large casserole dish and cover. Bake for 20 minutes in a 350° oven.
Recipe provided by Pork Checkoff.