1. Heat the olive oil in a wide saute pan over medium heat, and saute the leeks and garlic until soft. Add the sliced mushrooms and saute until softened and dry. Add the creme fraiche, thyme and black pepper and continue to cook for another three minutes until the mixture has thickened.

2. Scoop mushroom mixture into a bowl and add in a few cracks of black pepper, lemon juice, worcestershire sauce (if using), Tabasco and parmesan. Taste and make sure it is well seasoned. If not, add salt to taste. Allow this mixture to cool completely.

3. Preheat oven to 220C. Line two baking sheets with baking paper. Remove the puff pastry sheets from the freezer and let them thaw for 10 to 15 minutes so they are just pliable. Dust each sheet with a little flour and using a rolling pin, roll them out bit thinner. Cut each sheet into two rectangles.

4. Place a sixth of the filling slightly off-centre on one of the pieces of dough. Top that mound of filling with a sixth of the grated cheese.

5. Beat the egg with two tablespoons water in a small bowl and brush some of the egg wash around the edges of the pastry, then fold the pastry in half over the filling, pressing that side onto the egg wash so that the pastry sticks together, forming a square. Press the tines of a fork around the three unfolded sides to seal securely. Cut a few slits on the top of the pie to let air escape and place onto prepared baking sheets. Repeat with remaining dough and filling.

6. At this point the pies can be frozen for a later use or baked immediately. If baking immediately, brush the tops of the pies with more egg wash, place in the oven and bake for 20 to 30 minutes, rotating the pan halfway through. They should be deeply golden brown and you should see the mixture bubbling inside through the slits of the crust. Remove from the oven and allow to cool for a few minutes before serving warm.

Find more of Danielle Alvarez's recipes in the Good Food Favourite Recipes cookbook.