For the potato cake
6 large potatoes (about 1¼kg), scrubbed clean
150 ml olive oil
16 spring onions or 2 large bunches scallions (about 200g), trimmed and thinly sliced
6 garlic cloves, peeled and thinly sliced
Salt and black pepper
160 ml of double cream
3 large eggs plus 1 yolk, beaten
85g Parmesan, finely grated
3 tbsp finely chopped preserved lemon or 1 tablespoon fresh lemon zest
1 tsp ground turmeric
140g mature Cheddar, roughly grated
200g feta (preferably Greek), roughly crumbled
For the pea and thyme filling
200g frozen peas, thawed
1 tbsp chopped fresh thyme leaves, plus a few extra sprigs to garnish
For the red pepper and harissa filling
250g roasted red peppers, drained, patted dry and roughly chopped
20g roughly chopped fresh coriander, plus 1 tbsp for garnish
3 tbsp harissa paste or 1 tsp red-pepper flakes
1. Add the potatoes to a large pot and top with enough water to cover by about 4cm. Bring to a boil over medium-high, then lower the heat to medium, cover with a lid and cook until easily pierced with a knife, about 30 minutes. Drain well. Once cool enough to handle, peel the potatoes (saving the skins for another use), and transfer them to a large bowl.
2. While the potatoes are cooking, add half the olive oil to a large 30cm cast-iron frying pan or an ovenproof dish that is at least about 8cm deep. Heat over medium. Once hot, add the spring onions and garlic and cook, stirring occasionally, until soft and lightly coloured, about 6 minutes. If making with peas, add the peas and thyme; if making with peppers, add the peppers, cilantro and harissa. Add ½ tsp salt and plenty of pepper, stir to combine and set aside.
3. Heat the oven to 230 degrees Celsius (non-fan).
4. Add the cream, eggs and yolk, Parmesan, preserved lemon, turmeric, half the Cheddar and ½ tsp salt to the potatoes in the large bowl. Use a potato masher to break everything down to a rough mash that is still a bit lumpy. Add the feta and the spring onion mixture and fold everything together.
5. Wipe the pan/dish clean, add the remaining olive oil, then transfer the pan/dish to the oven for about 5 minutes to heat up. Remove from the oven and carefully add the potato mix. Level the top, sprinkle with the remaining Cheddar and a few sprigs of thyme, if using, in the centre and return to the oven.
6. Reduce the oven temperature to 205 degrees and bake the cake until golden and bubbling, 25 to 30 minutes. Remove from the oven and set aside for 15 to 20 minutes to firm up before serving. Sprinkle with the extra cilantro, and serve warm, spooned directly from the pan. – New York Times