To make the pesto, heat a large non-stick frying pan over a medium high heat. Add the pine nuts and toast for 1-2 minutes, stirring constantly until lightly browned. Remove the pan from the heat and tip the pine nuts onto a plate to cool.
When cool, put the pine nuts, basil leaves and garlic clove in a small food processor or large pestle and mortar. Pulse or pound the ingredients until you have a fairly smooth sauce, gradually adding the extra virgin olive oil. Transfer the pesto to a small bowl and stir in the grated Parmesan and enough water to give a soft, spoonable consistency. Season the lamb leg steaks on both sides with a small pinch of salt and plenty of freshly ground black pepper. Heat the oil in the frying pan used to toast the pine nuts. Add the lamb leg steaks and cook over a medium-high heat for 2-3 minutes on each side until nicely browned on the outside but slightly pink and juicy inside.
While the steaks are cooking, make the salad. Toss the cannellini beans with the rocket, tomatoes, sliced red onion and a good squeeze of lemon juice. Serve the lamb topped with spoonfuls of the pesto and the beany salad. Stir the lemon juice into the warm pan juices and dribble over the lamb and salad just before serving.
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