Chicken with Tarragon and White Wine

Name: Chicken with Tarragon and White Wine
Ingredients: 1/4 cup vegetable oil; 1 (4 1/2-pound) chicken, cut into 8 pieces; Kosher salt and freshly ground black pepper; Flour for dusting; 1 1/2 cups (about 10 ounces) cipollini or pearl onions, trimmed and peeled; 4 cloves garlic, halved; 1 cup white wine, such as Riesling; 3 cups low-sodium chicken broth, plus 1/3 cup; 1/2 cup chopped fresh tarragon leaves, plus 2 tablespoons; 2 tablespoons all-purpose flour; 2 tablespoons unsalted butter