Roast the walnuts in the oven at 180 ° C for about 8-10 minutes until they smell really nice and turn light brown. Allow to cool, remove peeled parts of the shell and roughly chop. Melt 80 g of raw cane sugar in a pan over moderate heat, add about 2/3 of the walnuts and caramelize, let them cool on baking paper and crumble again into a coarse brittle. Cold spots.
Puree the remaining walnuts with 250 ml milk, bring to the boil while stirring, simmer gently for approx. 2 minutes, allow to cool and strain through a hair sieve. In a stainless steel bowl suitable for water bath, beat 4 egg yolks with 40 g of raw cane sugar, 1 packet of vanilla sugar and a good pinch of salt until frothy, add 70 ml of maple syrup and continue beating briefly. Bring the nut milk with 250 ml of cream to the boil, gradually whip it into the egg yolk mixture, place the whole thing in a water bath and let it thicken slightly with a wooden spoon while stirring constantly (peel off to the rose), the temperature should be around 80 ° C for several minutes be. Chill in the refrigerator for a few hours.
Before making the ice cream, beat the nut mass with the hand mixer for 4 - 5 minutes and fold in another 250 ml very stiff whipped cream. Season to taste, if necessary sweeten with maple syrup (or variant, see below). Freeze in the ice cream maker and, when the mixture is already a bit frozen, add the caramelized walnuts.
Variant for those who like it sweeter:
Add the crumbled meringue of 1 - 2 egg whites together with the caramelized walnuts. For this meringue, whip 2 egg whites with 100 g raw cane sugar until very stiff, spread on a baking sheet lined with baking paper and dry at 100 ° C for approx. 90 minutes (until lightly browned). Let cool, crumble and freeze before adding. The meringue significantly improves the portioning ability of the frozen ice cream mass!