Chicken with apples and onions in the oven

Ingredients:

• 6 chicken legs (about 1.3 kg)
• 1 tbsp mustard powder
• 2 tablespoons extra-virgin olive oil
• 220 g pearl onions
• 2 tablespoons unsalted butter
• 2 tbsp. flour
• 1/3 cup dry white wine
• 0.5 cup apple cider (unfiltered apple juice without sugar)
• 0.5 cups lightly salted chicken broth
• 2 Granny Smith apples, cut into pieces
• 1 tbsp tarragon vinegar or white wine vinegar
• 3 tbsp chopped fresh herbs (chives, tarragon and/or chervil)

Preparation:

1. In a large bowl, combine the chicken with mustard powder, 1 tablespoon olive oil, 2 teaspoons salt, and a pinch of freshly ground black pepper. Cover and refrigerate for 30 minutes.
2. Preheat oven to 260°C. Place pearl onions in a small bowl and pour boiling water over them. Let sit for 5 minutes, stirring occasionally, then drain. Trim the root ends of the onions and peel off the skin.
3. In a large ovenproof skillet, heat the remaining 1 tablespoon olive oil over medium-high heat. Add half the chicken thighs, skin side down, and cook until golden brown, 4-5 minutes. Flip and cook on the other side, about 3 minutes. Transfer the thighs to a plate and repeat with the remaining chicken.
4. Wipe out the skillet, then melt the butter over medium heat. Add the pearl onions and cook, stirring, until golden brown. Sprinkle with flour, tossing to coat. Stir in the white wine and cook for 1 minute, then whisk in the apple juice and broth; bring to a simmer. Remove from heat; arrange the chicken legs, skin-side up, on top of the onions and arrange the apples around them. Transfer the skillet to the oven; roast until the chicken is crispy and a thermometer inserted into the thickest part of the thigh registers 165°F (74°C), 25 to 30 minutes.
5. Transfer the chicken to a platter and stir in the vinegar and herbs. Arrange the onions, apples, and sauce around the chicken.