Preheat the oven to its highest temperature (about 250°C/Fan 250°C/Gas 10). Pour the oil into a large roasting tin that will easily fit the aubergines in one layer. Wash and dry the aubergines, slice the stalk tips off, then cut each one in half. Add them to the tin and mix well so that every piece is glossed. Roast on the top shelf for 15 minutes, or until they colour and shrivel. Remove from the oven, add the onions, toss well and set aside (this is so that the onions receive a little of the residual heat before the next stage). Turn the oven down to 170°C/Fan 150°C/Gas 3½.
Meanwhile, put the cream, milk, garlic, oregano and chilli in a saucepan and place over a medium heat. When it’s nearly simmering, add the Parmesan and stir until melted and
fully incorporated. Remove from the heat. Tip the aubergine and onions into a smaller ovenproof dish so that they fit in 1–2 layers. Pour the cream mixture over the top and gently stir it in. Bake for 20 minutes or so, or until the aubergines are soft and yielding and the cream is thick and lightly golden on top. Finish with a squeeze of lemon and a sprinkle of zest as a seasoning to lift and refresh the dish, rather than to make it taste of lemon.
You could prepare this in advance, stopping once you’ve mixed the aubergines and cream. If you do that, add another 5–10 minutes to the final cooking stage and don’t add the lemon until just before serving.
ALONGSIDE: (other recipes from On the Side) Flower sprouts with lemon and anchovy butter (page 30); Rosemary and chestnut sprouts (page 34); Sweet cauliflower greens (page 38); Purple sprouting broccoli with tarragon (page 42); Hasselback potatoes with bay and caraway (page 172)