Cook the onion in 1 tbsp olive oil in a large pan until soft
(about 5 minutes). Add the potato and stock and simmer
until the potato is tender (about 10 minutes).
Add the broccoli
and cook for 3-4 minutes until just tender but still bright
green. Add half the cheese and whizz to a smooth soup in
a blender. Season then serve with the rest of the cheese