Heat the butter in a pan. Sauté the onion for approx. 3 mins. Add the pears and cook for approx. 2 mins., add the pear schnapps, reduce almost completely, set aside.
Empty the cheese mixture into the fondue pot. Mix the cornflour into the wine and stir in. Bring to the boil while stirring, reduce the heat, continue to simmer until the cheese has melted and the fondue is creamy.
Stir in the pears, season.