Roast sweet potato, pineapple and bean pastries with tahini, chilli and lemongrass dressing

Ingredients

flour, for dusting
300g/10oz ready-made puff pastry
1 free-range egg yolk, beaten
1 tbsp sesame seeds (a mixture of black and white is nice; poppy seeds are also good)
2 sweet potatoes, scrubbed
½ small pineapple, peeled and cored
2 tbsp extra virgin olive oil
salt and freshly ground black pepper
200g/7oz green beans, trimmed
For the dressing
10cm/4in piece of lemongrass stalk, base and outer two layers discarded, thinly sliced
½ red chilli, sliced (use more or less to taste)
1 garlic clove, peeled
½ tsp salt
small handful coriander leaves
3 tbsp tahini
4 tbsp lemon juice
3 tbsp extra virgin olive oil

Method

1. On a lightly floured surface, roll the pastry out into a 15x24cm/6x9in rectangle and allow to rest in the fridge for about 30 minutes.
2. Preheat the oven to 220C/425F/Gas 7 and line two baking sheets with baking parchment.
3. Take the pastry from the fridge and cut it into four equal-sized rectangles, measuring 15x6cm/6x2in. Put them on one of the prepared baking sheets, brush with the beaten egg yolk and sprinkle with the sesame seeds.
4. Bake in the middle of the oven until they are golden and well risen, around 15-18 minutes, then turn the oven down to 200C/390F/Gas 6 and cook for another eight minutes or so, while you prepare the rest of the dish.
5. Cut the sweet potatoes and pineapple into slices 1cm/½in thick and lay on the other baking sheet. Brush with one tablespoon of the olive oil, season with salt and freshly ground black pepper, and place in the top of the oven.
6. Once you've put the tray of potato and pineapple in the oven, take the pastry out, carefully split it in half horizontally and separate the tops and bottoms. Return them to the oven to dry them out for five minutes, then remove and place on a cooling rack.
7. Once the sweet potato is cooked (insert a knife into it to test), remove the tray from the oven.
8. Heat a heavy-based pan, ideally non-stick, and fry the pineapple in the other tablespoon of olive oil to colour it on both sides, then place back on the baking sheet.
9. While all of this is cooking in the oven, make the dressing. This is best done with a pestle and mortar, or you can chop everything very finely. Pound the lemongrass, chilli, garlic and ½ teaspoon of salt to a coarse paste. Pound in the coriander and then mix in the tahini, lemon juice and olive oil.
10. Blanch the beans and keep them hot.
11. To serve, place a pastry bottom on each of the four plates, then pile the sweet potato and pineapple on top. Add the beans, then drizzle with the dressing and, finally, put a pastry lid in place. Eat while still warm.