In a heavy saucepan, gently saute the onions in the Ladismitter Cultured Butter until soft and translucent. Add milk and bring to a simmer. Stir in Ladismith Cheddar until melted and smooth.
Whisk together corn-flour and whiskey until smooth. While constantly stirring, slowly pour whiskey mixture into cheese mixture and continue to cook until thickened.
Pour the mixture into a fondue pot or heat-proof bowl. Serve with rye or onion bread cubes as dippers.