Add the double cream, condensed milk and hazelnut cream to a bowl.
Whisk on a low-medium speed until the ingredients are smooth and even.
Turn the whisk up a bit higher and whisk till the mixture is starting to thicken and is lovely and smooth. It'll only take 1-2 minutes. It doesn't need to be extremely thick, it just needs to be smooth and starting to thicken.
Alternatively, you can whip the cream up to soft peaks, and fold the ingredients together.
For Assembly
Melt the 125g hazelnut cream until smooth - this takes 20-30 seconds in the microwave. Break the chocolate and bueno into chunks.
Add 1/3 of the ice cream mixture to the tin/tub and swirl through 1/3 of the melted spread and chocolates.
Repeat twice more so all the ingredients are used up.
Put the tub/tin your freezer till frozen and firm and enjoy!