Boil the brocolli until soft.
Lightly fry the leeks in olive oil or butter until soft, wilt the spinach in a small amount of olive oil.
Season tuna steak with salt and pepper fry in a small amount of olive oil for a couple of minutes on each side until cooked to your liking. Leave to rest while you make the brocolli mash.
Drain the brocolli, add tablespoon of cream cheese, large handful of grated cheddar, salt and pepper and blitz with hand blender until smooth.
Mix spinach and leeks together before serving.