Place the walnuts under a grill and toast gently until slightly coloured. Do not leave unattended as the nuts brown quickly. Place the garlic and pea shoots in a blender and process until smooth. Add the toasted walnuts and blend briefly. Do not over process, as the nuts will take on a floury consistency. Turn the pea shoot mixture into a bowl then add the parmesan. Gradually add the olive oil until you have reached a thick coating consistency. You may not need all of the olive oil. Season with salt and pepper to taste.
This sumptuous pesto is best served as a sauce simply stirred through cooked tagliatelle, accompanied by a baby leaf salad.