Fill and boil the kettle. Pour the hot water into a large pan and pop it on a medium heat. Add a pinch of salt and bring back up to the boil. Tip in the pasta and cook for 7 mins with the lid on (keep your eye on the pan and turn the heat down if it looks like it may boil over).

While the pasta cooks, trim the dry end off the broccoli. Chop the broccoli into small bite-sized florets and cut the stalk into matchsticks.

Grate the cheddar and pop half in a bowl. Stir in the crème fraîche and mustard. Add a good pinch of salt and pepper. Preheat your grill to a medium-high setting.

When the penne has cooked for 7 mins, add the broccoli and cook with the pasta, lid off, for 3 mins till the pasta and broccoli are just tender. Scoop out a mugful of water (mind your fingers, or use a ladle) then drain the pasta.

Tip the pasta and broccoli back into the pan and add the crème fraîche mixture. Trickle in some of the pasta water so that the sauce is slightly loose and coats the pasta well. Taste and add more salt or pepper if you think it needs it.

Tip the creamy pasta into a medium ovenproof dish. Scatter over the remaining cheddar and the breadcrumbs. Slide under the grill for 5 mins till the dish is bubbling, the top is golden and the cheese is melting.

Serve the mac & cheese with generous handfuls of watercress and a good crack of black pepper over the top.