Mushroom Leek and Egg Tart

Heat the oven to Gas Mark 5, 190oC (375oF)  

Beat one egg in a small bowl for the egg wash. 

To prepare the pastry: Lay the puff pastry out a large baking sheet.  Cut a 2 cm strip from the perimeter of the puff pastry from each of the four sides. Brush the remaining puff pastry with the egg wash then prick all over with a fork to prevent puffing. Place the pastry strips along the edge of all four sides to form a border that is raised, gently pressing to seal. Trim the excess and brush the border with the remaining egg wash. Chill in the fridge for 5 minutes. 

Transfer the baking sheet to the oven and bake until the pastry is puffed and golden. This will take approximately 10 minutes.  

While the pastry is baking, heat half the oil and butter in a frying pan until gently foaming. Cut the leek in half lengthways then thinly slice and add to the frying pan.  Cook over a medium high heat, stirring and shaking the pan occasionally, until the leeks soften and turn pale golden at the edges. Transfer to a bowl.  

To cook the vegetables: Add the remaining oil and butter to the frying pan. Then add the mushrooms and cook for 4-5 minutes until they soften. Add back in the leeks and the thyme and season. 

Mix the crème fraîche, mustard and lemon zest in a small bowl and season with salt and pepper. Working within the border, spread this mixture over the pastry.  

Spoon the leek and mushroom mixture over the surface of the pastry.  Make 4 dips for the eggs then crack the eggs into them. Sprinkle over the cheese. Bake until the egg whites are firm and the yolks are still runny. This will take about 15-17 minutes.  

To serve: Sprinkle over some chives. Cut the tart into quarters and serve immediately with a green salad.