Cut 1 large cauliflower into florets and discard large stalks.
Chop 1 medium onion.
Peel & chop 1 large potato into chunks.
Melt butter in a large pan, add onion, potato and cauliflower.
Put on a lid & sweat gently for 10 mins.
Add about a litre of chicken or vegetable stock.
Bring to the boil, add ½ litre whole milk & return gently to the boil.
Add cream if you want the soup rich.
Season to taste & simmer for 10-15mins.
For extra smoothness pass through a seive.
Saute sliced mushrooms in olive oil, season and spoon the mushrooms into the centre of each bowl of soup.