Cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Add the broccoli 5 minutes before the end of the cooking time and cook until just tender. Drain and return to the pan.
Meanwhile, stir together the stock, mustard and crème fraîche in a jug, then mix together with the pasta, broccoli, ham and half the Cheddar and season. Spoon into an ovenproof dish and scatter over the remaining cheese.
Place in a preheated oven, 200°C (400°F), Gas Mark 6, for 15 minutes or until golden, bubbling and cooked through.