Heat oil in the saucepan. Add the garlic, leeks, celery and parsnips. Cook for about 5 minutes.
Add the split peas, ham hock, herbs, 3L water and 1 tsp salt. Bring to the boil, then turn down to asimmer, cover and cook for 1 1/2 hours.
Allow the soup to cool, then remove the ham hock, and spirgs of thyme. Leave the bay leaves in the soup.
Puree the soup with a hand held blender.
Remove the skin from the ham hock and discard. Remove the meat from the bone and shred it wih your fingers, or chop it into small pieces.
Add the ham pieces to the soup, and reheat (save few pieces to put on top). Season before serving. Add croutons, a few thyme leavs and ham pieces.