Use a baking tray and a 20cm round, fluted loose-based quiche tin. Sift flour and a pinch of salt into a large bowl. Add the chilli and thyme, then make a well in the centre. Whisk the egg, oil and water and add to the dry ingredients; mix quickly with a fork to make a dough.
Place dough on a lightly floured work surface; knead briefly just until smooth. Place in a dry bowl, cover with a damp cloth towel and leave to rest for about 30 minutes before rolling out.
For the filling, cook potatoes in boiling water for 10–12 minutes or until almost tender. Steam leeks over the potatoes for 6–7 minutes, until tender. Drain thoroughly and leave until cool enough to handle.
Preheat oven to 200 degrees C and put the baking tray in to heat. On a lightly floured work surface, roll out pastry thinly to line the flan tin. Scatter half the cheese in the case.
Thickly slice the potatoes and toss with the leeks, remaining cheese and chives. Season with salt and pepper. Arrange half the potato and leek mixture in the pastry case. Scatter rocket on top, then add the rest of the potato and leek mixture.
Lightly beat eggs in a jug. Heat milk to just below boiling point, then add to the eggs; whisk gently to combine.
Place tin on the hot baking tray. Pour the warm egg custard into the case. Bake for 10 minutes, then reduce oven temperature to 180 degrees C. Bake a further 30–35 minutes or until the filling is lightly set. Leave quiche in the tin for 5 minutes. Serve warm.
Chillies contain more vitamin C weight for weight than citrus fruit. But the quantity of chillies usually eaten means the overall intake of this vitamin is not huge. * Rocket, like other dark green leafy vegetables, is a good source of folate, a vitamin involved in the production of red blood cells. * Like many other cheeses, gruyère has a high saturated-fat content: this makes it a good source of fat-soluble vitamins such as A and D.