Cook the macaroni in boiling salted water for 8 minutes then add the broccoli florets and cook for a further 2 minutes. Drain in a sieve and return to the pot.
Whilst the macaroni is cooking add the milk, flour and mustard to a medium sized saucepan. Bring the mixture to the boil, then turn it down to simmer and whisk it thoroughly until you have a smooth and thickened white sauce. Then add 75g of the cheese and again whisk until smooth.
Add the cheese sauce to the pot with the macaroni and broccoli and stir together well to combine.
Pour the contents of the saucepan into an oven proof dish, sprinkle with the remaining cheese and place onto the middle shelf of your oven.
Bake for approximately 15 – 20 minutes until the cheese has browned slightly and is bubbling.
Serve with a green side salad of lettuce, cucumber and spring onions.
If using frozen broccoli allow it to defrost completely first.