Peel and pip the butternuts, and cut it into about 5cm square chunks.
Peel and chop the onions quite finely.
Chop the garlic very finely, or push through a garlic press.
Halve the Jalapeno pepper or green chillies and scrape out all the pips. Chop the green flesh very finely.
Put the onions, garlic and chillies into the melted butter in a saucepan on a moderate heat and cook until the onions are soft and transparent. Add the lemon juice and chicken stock and stir until well mixed.
Add the water and the cubes of butternut, and simmer until the soup is thick and all the ingredients are well blended together, about 1 hour.
Liquidise with a Bamix or a food processer.
Serve hot.
Swirl a tablespoon or two of fresh cream into the centre of each bowl of soup just before serving.