1. Preheat the oven to 180°C. While you bring 150ml of water to the boil place the couscous in a bowl and add a good pinch of salt. Pour over the boiling water then cover tightly with clingfilm. Leave for five minutes before removing the clingfilm and fluffing up with a fork. Mix in the coriander and mint along with the lemon juice and chilli flakes. Check seasoning and adjust to taste. Set aside.
2. Quarter the washed carrots lengthways and place into a bowl along with the sliced red onion. Add in a good pinch of salt along with the white wine vinegar and set aside to pickle.
3. Take the filo pastry and lay the sheets out flat on a work surface. Cut into twelve equal squares and brush with egg yolk. Divide the feta cheese equally between each, placing as centrally as possible, then take the corners of each square of pastry and bring inwards, gently pinching together to create small parcels. Place the parcels onto a lined baking tray and place the tray into the pre-heated oven. Bake for 10-15 minutes, or until the pastry is lightly golden and crisp.
4. Tip the pistachios onto a baking tray and toast in the oven for five minutes. Allow to cool slightly, then crush roughly with a pestle and mortar or the back of a knife. Mix the harissa with the yoghurt and add salt to taste. Peel and slice the pink grapefruit and keep ready for serving.
5. To serve, divide the watercress between four plates. Drain the pickled carrots and arrange on top. Pile on the couscous then add in the grapefruit slices. Drizzle the lot with the harissa yoghurt and sprinkle with pistachios before serving with the warm feta parcels.
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