Mix the potatoes, cornflour and salt in a bowl, spread onto a baking tray lined with baking paper.
Bake for approx. 20 mins. in the centre of an oven preheated to 220°C.
Rub the garlic around the fondue pot. Add the Gruyère, Cheddar and cornflour, mix well. Pour in the wine. Bring to the boil while stirring, reduce the heat, continue to simmer until the cheese has melted. Stir in the whiskey and thyme, continue to stir until the fondue is creamy, season.