Combine the cheeses. Take a scant tablespoon of risotto, form it into a ball in your hand, then make an indentation in the ball. Take a small piece of the cheese mixture and press it into the risotto, then form the risotto into a ball again around the cheese. Whisk the egg and milk together, then coat the balls by dipping them first in the flour, then the egg & milk and finally the breadcrumbs. Chill for at least 20 minutes before frying. Heat a little oil or butter in a large saucepan, add in the onions and cook them gently for 7–10 minutes until they become translucent. Add the garlic, sunchokes and wine, bring to the boil, then lower the heat, cover with a piece of baking parchment and simmer for 8-10 minutes. Add the stock or water, bring it back to the boil, then lower the heat, put the lid on and simmer for 15-20 minutes, until the sunchokes are soft. Blend the soup to fine purée, then pass this through a sieve and return it to a saucepan. Add the cream and reheat gently. Do not allow the soup to boil. Just before you serve, stir in the truffle oil. While you are reheating the soup, heat some vegetable oil to 170°C/325°F in a large saucepan or electric deep-fryer. Drop in the chilled risotto balls and fry them for 2–3 minutes until lightly coloured. Divide the soup between 4 serving bowls and place a deep-fried risotto ball in each one. Sprinkle some chives over the top and serve.