1. Heat your oven to 180°C/Fan 160°C/Gas 4. Quarter the cherry tomatoes and spread them out on a baking tray. Season with salt and pepper and slide into the oven to roast for 20 mins.
2. Set a heavy-based frying pan (preferably ovenproof) over a medium-high heat to warm up. Rub the lamb steaks with a little olive oil and a good pinch of salt and pepper each. Carefully add them to the hot pan and cook for 2-3 mins on each side. Slide the pan into the oven for a further 8-10 mins to finish cooking the steaks. Frying pan not ovenproof? Just transfer the steaks to a baking tray. Once the lamb steaks have finished cooking, pop them on a warm plate, loosely cover with foil and rest for 5-6 mins.
3. Wipe the frying pan clean and set it back on the heat. Slice the aubergine in half lengthways then add it to the smoking hot pan. Cook for 6-7 mins on each side till very soft. Tip onto a board and cool for a few mins, then scoop the soft flesh out of the blistered skin and transfer the flesh to a food processor.
4. Drain and rinse the chickpeas. Tip them into the food processor. Peel 1 garlic clove and grate it in, along with the zest from the lemon. Squeeze in the juice from half the lemon. Add most of the oregano leaves, a little salt and pepper and 1 tbsp olive oil. Blend till smooth, add a splash of water if it seems too dry. Taste and add more salt, pepper, lemon juice or a glug more of olive oil, if you think it needs it. No food processor? See our tip below.
5. Finely chop the rosemary leaves and tip them into a mixing bowl. Peel and grate in the remaining garlic clove.
6. When the tomatoes have finished roasting, stir them into the garlic and rosemary, along with a pinch of salt and pepper and 1 tbsp olive oil.
7. Spoon the mash onto two warm plates and serve with the lamb leg. Finish with the tomato and rosemary salsa, the remaining oregano leaves and a drizzle of the lamb resting juices.
8. Gadget-free Mash
If you don't have a food processor, you can make the mash by cooking the aubergine till it's soft, then scooping the flesh into a bowl and mashing till smooth. Cook the chickpeas in hot water till tender, then add to the aubergine and mash them together. Stir in the grated garlic, lemon zest, lemon juice and choped oregano with a glug of olive oil and a pinch fo salt and pepper. The mash will be chunkier, but still as tasty.