- With the rack in the middle position, preheat the oven to 190 °C (375 °F). Line a baking sheet with parchment paper.
- In a bowl, combine the marmalade, butter, parsley, and mustard. Season with salt and pepper. Set aside.
- On a cutting board, with a chef's knife, cut the chicken backbones to open the chicken flat. Gently lift the skin from the breast and thigh without tearing it. Spread the marmalade mixture between the meat and skin. Place the chicken flat on the baking sheet, breast side up. Season with salt and pepper.
- Bake for 1 hour to 1 hour and 15 minutes or until a thermometer inserted into the thigh, without touching the bone, reads 82 °C (180 °F). Baste with the pan juices halfway through cooking. Keep the chicken warm and the cooking juices for the sauce.
- Meanwhile, in a small saucepan, melt the butter. Sprinkle with the flour and cook for 1 minute, stirring continuously. Add the orange juice and broth. Bring to a boil, stirring with a whisk. Simmer for 2 to 3 minutes. Add the pan juices from the chicken. Adjust the seasoning.