Heat the butter and sauté the onion, celery and cauliflower for approx. 5 mins. Add the stock, bring to the boil, then simmer for approx. 5 mins. Spread butter on the slices of bread and place on an oven tray lined with baking paper. Top with the garlic and parsley, season with salt.
Bake for approx. 6 mins. in the centre of an oven preheated to 220°C.