Nibblous | potato and cheddar soup

Ingredients

• 50g (1 3/4 oz) butter
• 2 onions, chopped
• 750g (1 1/2 lb) potatoes, peeled & chopped
• 3 cups (750 ml / 24 fl oz) chicken stock
• 1 1/2 cups (375 ml / 12 fl oz) milk
• 1 1/2 cups (185 g / 6 oz) grated vintage cheddar cheese
• cayenne pepper, to taste
• salt, to taste
• 2 tablespoons chopped walnuts
• 1 small celery stick, chopped
• 1 tablespoon chopped chives