Melt the sugar in a pan over a not too hot fire. When it is golden brown and liquid, add the whole walnuts and caramelize while stirring.
Place the caramelized walnuts on a baking sheet and leave to cool
Put the pan with the caramel leftovers back on the stove. Add maple syrup and 2 dl cream and bring to the boil. Simmer until all the caramel remains have dissolved. Then let it cool down.
Add the rest of the cream and put everything in the fridge for at least 2 hours.
Grind 2/3 of the walnuts and chop the rest into pieces.
Mix the walnuts with the liquid and freeze everything in the ice-cream maker.