Melt the butter in the fondue pot. Add the garlic, onion and tomatoes, briefly cook without colouring then moisten with the white wine. Add the cheese and bring to the boil over a low heat, whilst stirring continuously. Mix the cornflour and the kirsch and pour into the fondue. Continue to stir well, bring to the boil once again then season with the pepper and nutmeg. According to taste, one can flavour the fondue further with a pinch of marjoram or oregano. (To prepare the tomatoes concassée: Make an incision in the shape of a cross in the skin of the tomatoes, briefly immerse them in boiling water, refresh with cold water, then carefully peel them. Remove the seeds and cut the tomatoes into small dice).