1. Preheat the oven to 160~170℃ degrees. Spread the hazelnuts out in a single layer on a baking sheet and roast for 15~20min, or until the hazelnuts become fragrant.
2. Remove from the oven and let them cool down. Then roll the nuts with your hands to peel the skin off, or most of it at least. They don’t need to be perfect, so just try to get as much as you can.
3. Add the hazelnuts in your food processor, then process them until just coarse-grained. Set aside 30g from these processed hazelnuts and keep them for further use. Then add sugar (30g) and whole milk (2 tbsp). Continue to process until the remaining is creamy and smooth. Transfer the hazelnut paste into a medium bowl. Set aside.
4. In a bowl, add egg yolk. Pour the milk into the bowl little by little, and mix. Add sugar and mix.
5. Transfer the milk mix into a small pan and heat up to 75~80℃ over medium heat, turn the heat to low and simmer for 3min.
6. Using a fine mesh filter (your usual sieve will do), strain the milk into a heat-safe bowl, then add inverted sugar and glucose. Mix well to melt. Let it cool down completely.
7. Once the milk mixture is cooled completely, pour it little by little into the hazelnut past bowl. Mix well.
8. Add heavy cream and mix.
9. Transfer the ice cream mixture into your compressor ice cream maker and let it run according to manufacturer's instructions. It should take 40~60min, depending on how cold the mixture. In case, you should let it run until the mixture turns thick and creamy.
10.Meanwhile make "caramelized hazelnuts : Put the sugar in a small pan, and melt it completely. Over medium heat, shake the pan gently to redistribute the melting sugar, but do not stir sugar at this point. When the sugar dissolves, add the coarse-grained hazelnuts from #3. Stir continuously with a wooden spoon until the nuts are caramelized. Transfer it onto the baking paper. Once it is cold enough, crush them using a wooden stick or spoon. Set aside until the ice cream is ready!
11. Mix the caramelized hazelnuts to the ice cream.
12. Transfer the ice cream to a storage container, and let it freeze until you eat!