Leek & herb soufflé
Preheat the oven to 180°C/350°F/Gas mark 4. Lightly grease a 900ml/1 1⁄2pt soufflé dish with vegetable oil.
Heat the olive oil in a frying pan. Add the leeks and sauté over a medium heat, stirring occasionally, for 2–3 minutes.
Add the stock to the pan, reduce the heat and simmer gently for a further 5 minutes.
Put the walnuts in a blender or food processor, and chop finely. Add the leek mixture to the nuts, and process briefly to form a purée. Transfer to a bowl.
Mix together the egg yolks, herbs and yogurt until thoroughly combined. Pour the egg mixture into the leek purée. Season with salt and pepper, and mix well.
Put a baking tray into the oven to warm. In a separate bowl, whisk the egg whites until firm peaks form. Gently fold the egg whites into the leek mixture. Spoon the mixture into the prepared dish, and place on the warmed baking tray. Bake in the oven for 35–40 minutes until risen and set. Serve immediately