Jerusalem artichoke soup

In Süd-Tirol I had lots of Jerusalem artichoke, once as a soup and then as puree. Today I saw them at the grocer's and they were fairly cheap, so maybe it's the season now.
In French they are called topinambour, in Flemish aardpeer (= earth-pear).
The taste is delicious, a bit like artichoke. I improvised this soup.


1 kg Jerusalem artichoke, peeled and chopped
1 leek, chopped
1 small onion, chopped
1 turnip, peeled and chopped
olive oil
2 garlic cloves, chopped
thyme & bay leaves
1 tsp sugar
a little veg. stock (in cubes or paste)

Fry the onion in olive oil for a few min. Add garlic and fry until it gives off its scent. Add leek and fry for a few more min. Add turnip and Jer. artichoke, thyme & bay leaves and fry for a few more min.
Add boiling water and bring to the boil.
Add pepper, salt, stock and sugar.
Let it simmer on low heat for 10 min.
Mix the soup with a hand mixer.
The soup has a really nice creamy texture.