Preheat the oven to 200C/400F/Gas 6.
Heat a small saucepan over a low to medium heat, crumble in the cheese and add the cream and mustard. Stir until the cheese is melted, then season, to taste, with salt and freshly ground black pepper.
Arrange the blanched broccoli in an ovenproof gratin dish and pour over the cheese sauce.
Bake in the oven for 5-10 minutes, or until the cheese mixture is golden-brown and bubbling.
