Fry the bacon in a large pan over a medium heat for 5 minutes. Add the potatoes, leeks, stock, marjoram, thyme and nutmeg. Cover and simmer, stirring occasionally, for 20 minutes. Season with salt and freshly ground black pepper.
STEP 2
Meanwhile, in a small pan, cook the onion in the butter over a medium heat for 5 minutes. Add the sugar and allow the onion to caramelize, this may take a few minutes.
STEP 3
In a food processor, puree the bacon and vegetables, in batches, until smooth. Return the soup to the pan, and stir in 150ml boiling water.
STEP 4
Ladle the soup into bowls, top each with grated Emmental, some caramelised onions and serve with warm crusty bread.