First step in this recipe is to make mushroom duxelles. For this, start by finely dicing the brown onion and garlic then adding to a large wide based pot or pan with the butter to lightly caramelise. Add the bay leaf and thyme and continue to lightly cook this mixture until the onions and garlic have lightly caramelised and softened. In a blender, add the mushrooms and pulse blend to achieve a fine dice (not a paste). Alternatively, this step could be done by chopping by hand, but ain’t nobody got time for that!
Add the mushrooms to the onion and garlic mixture and continue to cook until the liquid reduces and is almost completely gone - this usually takes an hour over a medium heat. Make sure to stir mushrooms routinely to stop them sticking to the pot. Once this mixture is cooked and not looking ‘wet’, remove it from the pan and chill until completely cold, remove the bay leaf and thyme stems and discard.
Peel the pumpkin and, using the solid end of the vegetable (non seed end), slice on a meat slicer to 1-2mm sheets, laying each sheet onto the last as you slice them. Eventually, if successful you will have a stack of round pumpkin sheets looking almost like a stack of crepes. Slice the truffle either on the meat slicer or on a truffle slicer and tuck these sliced between the pumpkin sheets.
Press the pumpkin sheets down with force to flatten any curling edges then trim to achieve a neat round slightly compressed stack. With your hands take a little of the mushroom duxelles and begin to cover the pumpkin stack until completely covered in a 1cm thick layer of mushrooms on the top and sides.
To make the egg wash for the pastry, in a small bowl whisk (with a fork) the egg yolk and water together, then strain through a fine sieve to remove any unwanted membrane, shell or bubbles. Set aside until you are ready to assemble the pie.
On a baking tray lined with baking paper place one sheet of puff pastry down, then brush lightly with egg wash. Place the pumpkin/mushroom disc gently in the centre of the egg washed puff pastry then gently place another sheet of pastry directly over the top.
With very clean hands gently press the top layer of pastry down to meet the egg washed bottom layer and work your hands around to shape the pastry around the pumpkin/mushroom disc until all tucked in and completely sealed, being careful not to trap large air pockets between the sheets. Once this step is done return the entire pie to a refrigerator just to let the pastry cool down in case your hands have warmed it slightly.
Once rechilled, using a large ring cutter or knife cut the excess pastry from the sides to create the round ‘pie’ shape (worth googling this if you are unsure of what I’m saying) once the shape is cut, brush the entire pie with egg wash and place back in the cool room for the egg wash to set. Once set repeat this process two more times to create a good even coating of egg wash.
Score the pie with your desired patterns making sure to cut an air hole in the top so steam/moisture can escape while cooking. Again, if unsure best to google ‘decorating pithiviers’ and copy what people have done.
Pre heat your oven to 210 C and, once hot, bake the whole pie for 25 minutes, then turn the heat down to 160 C and bake for a further 15minutes or until the pastry is evenly golden top and bottom. Remove from the oven and let stand for roughly 15 minutes then serve. Best served with a green salad and chutney or onion gravy.
