PREPARATION

1. Roast the butternut squash in the oven (200 C) until soft. Let it cool slightly, mash and squeeze out any excess water in a tea towel.
2. Heat a little olive oil in a large frying pan, add the leeks and onion. Cook for 10 minutes until soft and sweet.
3. Add the garlic, fennel seeds and chilli flakes and cook for another five minutes. Tip into a bowl to cool and add the mashed and drained squash, chestnuts, gruyere, mustard and a generous pinch of salt and pepper.
4. Preheat the oven to 220C.
5. Unroll the puff pastry on a floured surface, then cut in half lengthways so you have two long, thin rectangles.
6. Add half of the squash mixture along the side of your rectangle in a long sausage shape leaving about 2 cm pastry on the edge. Egg-wash the 2 cm pastry side and the pastry over your sausage, letting it stick onto the egg washed side, pressing the two sides together to seal
7. At this stage, you can freeze the rolls until needed or go to the next step.
8. Put the little rolls on a baking paper-lined tray, brush with the beaten egg, then generously sprinkle with sesame seeds. Bake for 20-25 minutes, until golden and bubbling (or about 30 minutes when frozen).