Chestnut Soup With Bacon - Velouté De Chataignes Et Bacon

7 ounces cooked and peeled whole chestnuts
1 stalk celery, trimmed and finely chopped
1 small onion, peeled & finely chopped
1 small carrot, peeled and chopped
2 pints ham or vegetable stock
salt & freshly ground black pepper
1/2 pint creme fraiche or single pouring cream

For the croutons
4 ounces lardons or bacon, cubed
1/2 teaspoon finely chopped fresh thyme leaves
4 ounces day-old white bread, cut into small cubes
4 tablespoons olive oil

To make the soup, you simply place all the ingredients, except the crème fraiche or cream, in a large saucepan.
Season lightly with salt and pepper, bring up to simmering point, then put a lid on and simmer very gently for 45 minutes.
While that is happening, you can prepare the croutons.
Heat the oil in a large frying pan and cook the bacon gently for 5 minutes, then turn the heat up to its highest setting, add the cubes of bread, together with the thyme, and toss them around (keeping them constantly on the move) until they, and the bacon, have turned a deep golden brown colour and become very crisp and crunchy.
Take them out & leave them to cool on some absorbent kitchen paper.
As soon as the soup is ready, add the crème fraiche or cream & mix well - allow it to cool slightly, and then transfer it to a blender and purée until smooth. (You may need to do this in more than one batch, in which case, it is a good idea to have a bowl to put the soup in as it is ready.).
Re-heat the soup in the pan, season to taste and serve in warmed soup bowls, with the croutons, bacon and thyme sprinkled over.