Heat the oil in a large saucepan
Add the onion and fry for a few minutes until soft
Add the carrot and garlic and cook for a couple of minutes
Add the cauliflower
Add the stock and milk
Bring to the boil
Turn down the heat and simmer for about 15 minutes, until all the vegetables are soft
Place in a liquidizer or use a hand blender to make the soup smooth
Return to the pan and reheat
Add the mustard and stir
Remove from heat
Add the cheddar cheese and stir
Serve with good crusty bread