Preheat the oven to Gas Mark 1, 140ºC, fan120ºC. Peel 4 of the garlic cloves and put them whole in an ovenproof dish with half the rosemary, a pinch of salt and ½tbsp of olive oil. Put in the oven for 20mins to soften the garlic.
Finely chop the rest of the rosemary, and peel and crush the remaining garlic clove. Put them in a bowl, add half the lemon zest and juice, season. Add 2tbsp of the olive oil and mix well, then add the lamb to the marinade. Let this sit for 10mins while you make the white bean mash.
Drain the cannellini beans and put them in a pan over a medium heat to gently heat through. Remove the roasted garlic from the oven, discard the rosemary and mash the garlic with a fork, then add to the beans. Pour in the remaining ½tbsp of olive oil with the rest of the lemon juice and zest. Mash together, season and keep warm while you cook the lamb.
Preheat the grill to high. Put the lamb steaks on a grill pan and pour over any remaining marinade. Grill the lamb for about 5mins on one side, then turn over and grill for a further 5mins. Remove from the grill and allow them to rest while you warm the pitta breads under the grill.
Serve the lamb with the bean mash, the warm pitta breads and salad leaves.
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