Remove the meat from the fridge 30 minutes before cooking. Dry roast the pistachio nuts briefly in a non-stick frying pan. Put the rocket into a blender; add the pistachio nuts and the cheese, olive oil and salt and pepper. Blend until you have a chunky pesto sauce. Heat up the griddle (non-stick frying pan or barbecue). Brush the steaks with the remaining oil. Place on the hot griddle and cook for 3-4 minutes on each side until cooked to your liking. Leave to rest for 2 minutes. Place a small spoonful of pesto on each of the lamb steaks and serve the rest of the pesto separately. Serve with halved grilled tomatoes and fresh pasta. Chef's Tip: Don’t blend your pesto too much; the small pieces of pistachio nut will add a fabulous crunchy texture that is very different from ready-made pesto sauces.