250gbaby Portabellini or baby button mushrooms, sliced in half
40gParmesan cheese, grated
1large egg, beaten, for egg wash
Salt and pepper, to taste
For the béchamel:In a small saucepan over low heat, warm the milk. (Do not let any evaporate) In a second slightly larger saucepan, melt the butter. When melted, add the flour. Whisking constantly, cook for about 2 minutes. The mixture should not darken but turn a very light golden and smell like biscuits. Slowly pour in the warm milk, whisking constantly to keep the sauce smooth. Cook, whisking constantly, until the sauce thickens. Season generously with salt and add the mustard powder and nutmeg to taste. Pour into a bowl and cover with cling film on the surface to avoid creating a skin. Set aside in the fridge.
For the pies:Preheat oven to 200˚C. Line a baking tray with baking paper. Heat a drizzle of olive oil in a large frying pan. Sauté the mushrooms on high heat until golden brown. Season lightly and remove from the heat. Thaw the puff pastry and cut each sheet into quarters so you have 8 squares. Place them diagonally so they look diamond shaped on the lined tray. Spread a good dollop of béchamel on each piece of pastry, spreading it from the bottom corner to the top corner. Follow with a few pieces of pancetta and two spears of asparagus. Dot the cooked mushrooms over each piece. Finish with a sprinkle of grated Parmesan. Fold up the two side corners and seal them using a little bit of water on your finger tips. Egg wash the open pies and bake for 25 minutes until golden brown and cooked through. Serve with some lightly dressed micro greens and enjoy!