Ingredients

• 50g (1.7oz) butter
• 3-4 leeks, white and lightest green part only, thinly sliced
• 150g button mushrooms, sliced
• 2 teaspoons thyme leaves
• 1/2 cup (125g or 4oz) creme fraiche
• 1/3 cup grated Parmesan cheese
• 1/2 cup grated tasty cheddar cheese
• 1 1/2 sheets (approx 265g or 9oz) butter puff pastry
• 1 egg yolk, mixed with a fork

Method

Preheat the oven to 200 C (390 F). Melt the butter in a large frying pan over a moderate heat, when it starts to foam add the leeks and cook for 10 minutes, stirring at times. Add the mushrooms and thyme to the pan and cook for a further 5 minutes.  Season the mixture well with salt and freshly ground black pepper. Remove the pan from the heat and allow the leek to cool a little before mixing through the creme fraiche and grated cheese. Place the pastry sheets end to end on a baking tray, allowing for a .5cm overlap, press to seal.  Fold the edges of the pastry in creating a 1cm (just under 1/2 inch ridge). Spread the leek and mushroom mixture over the pastry, staying within the ridge. Brush the pastry edge with the egg yolk. Bake for 20 minutes or until pastry is golden and crisp. Serve warm or at room temperature.