In a large measuring jug, puree the cucumber and all the other ingredients up to and including the water. Season the soup, cover and leave to chill for approx. 2 hrs. Pour the soup into chilled bowls or glasses, drizzle with a little vinegar and olive oil.
Place the slices of baguette on a baking tray lined with baking paper.
Toast for approx. 5 mins. in the centre of an oven preheated to 220°C.
Spread the soft goats' cheese on the baguette slices, sprinkle with onion sprouts. Serve with the chilled summer soup.