Heat a large pan with the olive oil and add the chicken pieces. Fry off until golden and cooked through.
Boil a large pot of water; add the macaroni and broccoli, and simmer for 6-8 minutes until the macaroni is cooked to your liking.
Strain off and allow to cool slightly while you prepare the cheese sauce.
In a small saucepan, melt the butter. Stir in the flour until it forms a paste.
Gradually whisk in the milk, ensuring you are not left with any lumps of flour.
Bring the mixture to the boil, remove from the heat, and stir in 2 cups of the cheese.
Stir the sauce into the macaroni and broccoli mix.
Preheat your grill.
Place the mix into a large ovenproof dish. Scatter the breadcrumbs and remaining cheese over the top.
Place under the grill for 3-4 minutes until golden and crispy.