Lightly roast the cobnuts for about 10 minutes at 180C till they are turning golden

Put the parsley and basil, salt and garlic into a mortar and pound till the leaves start to break down.

Add the toasted cobnuts and continue to pound until you have a sticky paste

Gradually trickle in the olive oil, till the mixture is about the thickness of double cream

Stir through the grated cheese and add more olive oil till you have a sauce that drops easily from the spoon.

Store in the fridge till ready to use, for no more than 2-3 days. If you want to keep the pesto for longer, it will freeze without any problems