Roast the hazelnuts in a pan without fat. Bring the milk, cream and hazelnuts to the boil. In the meantime, mix the egg yolks with the sugar. When the milk and cream mixture boils, take it off the hob and filter 2-3 times through a hair sieve to remove the hazelnuts again (otherwise the ice cream tastes very dry and floury).
Then slowly stir the cream-milk mixture into the egg yolk and sugar mixture. Put everything back into the pot, heat it up, but don`t let it boil anymore. Let the mixture cool down.
Add the syrup and stir well. Put the mixture in the ice cream machine and process according to the manufacturer`s instructions.