Preheat the oven to 200C/400F/Gas 6.
To make the duck, heat an ovenproof griddle pan over a medium heat. Season the duck breast on both sides with salt and freshly ground black pepper, then place skin-side down onto the hot griddle to cook for 4-5 minutes. Turn the breast over and transfer to the oven to roast for 8-10 minutes, or until completely cooked through.
To make the sauce, place all the sauce ingredients into a frying pan and bring to simmer. Simmer for 5-6 minutes to reduce and thicken.
To serve, place the blanched broccoli into the centre of a large warm plate. Place the duck breast on top, then spoon the sauce around.