Potato gratin with coconut, chilli and lime
If you’re making the whole of today’s Christmas spread in one oven, bake the gratin ahead of time and reheat in a very hot oven just before serving. Top with the aromatics and zest just as you serve, and not before.
Prep 25 min
Cook 110 min
5 banana shallots, peeled and cut into 5mm-thick slices
2 garlic cloves, peeled and crushed
2 tbsp olive oil
Flaked sea salt and black pepper
1.4kg slightly waxy potatoes (I used yukon gold), skin on, cut into 5mm-thick slices (use a mandoline, ideally)
100g coconut cream, gently melted until liquid
3 limes – zest finely grated, to get 1½ tsp, then juiced, to get 60ml
200ml vegetable stock
For the aromatics
150ml olive oil
2 red chillies, finely sliced into rings
3 garlic cloves, peeled and finely sliced (on a mandoline, ideally)
2cm piece fresh ginger, peeled and finely cut into julienne strips
5 spring onions, green ends finely sliced at an angle
Heat the oven to 200C (180C fan)/390F/gas 6. Put the shallots, garlic, oil and a quarter-teaspoon of salt in a 28cm ovenproof saute pan on a medium heat. Fry for eight to 10 minutes, stirring occasionally, until soft and deeply golden, then tip into a large bowl. Keep the pan to be used again (no need to clean it).
Put the potatoes, coconut cream, lime juice, two teaspoons of salt and plenty of pepper in with the shallots and mix very gently, taking care not to break up the potato slices. Lay a quarter of this mixture in the saute pan – use any smaller or broken slices of potato at this stage, and save the larger, whole slices for the top – and spread out in an even layer. Lay the remaining potato mixture in a spiral on top of this base layer, with each slice at an angle and overlapping the next. Pour on the stock, cover tightly with foil and bake for 40 minutes.
Meanwhile, make the aromatics. Heat the oil in a medium pan on a medium flame, then gently fry the chilli, garlic and ginger for five minutes, stirring once in a while, until the garlic is just starting to turn golden. Add the spring onions, fry for two minutes more, until the garlic is a light golden brown and the chilli aromatic, then transfer to a plate with a slotted spoon, to stop them cooking further; reserve the aromatic oil.
Remove the gratin from the oven and discard the foil. Drizzle 60ml aromatic oil evenly over the top, then return to the oven uncovered and bake for 50 minutes more. Turn up the heat to 220C (200C fan)/425F/gas 7 for the last five minutes, until the top is golden brown and crisp.
Set aside to cool for 10 minutes, top with the fried aromatics, lime zest and a generous pinch of flaked salt, and take to the table.
Photograph: Louise Hagger for the Guardian