Trim one 13-inch and one 16-inch disc of puff pastry. You may need to overlap two sheets to achieve this, in which case use a rolling pin to ensure the two sheets adhere. Layer the pastry circles between baking paper, then reserve in the fridge until ready to assemble.
Preheat oven to 350°F. Whisk the yolks with milk to create an egg wash.
To assemble the vol au vent, line the inside of a 2.6 quart, 9-inch diameter mixing bowl (or similar) with aluminum foil, leaving enough overhang to cover the base. Fill the foil tightly with shredded baking paper. Tightly fold the excess foil over the base, then tip out of the bowl, creating a sealed dome.
Transfer the smaller pastry disc to a lined baking sheet. Place the foil dome in the centre and spray with baking spray. Brush the excess pastry with egg wash. Place the larger pastry disc on top, pressing gently to shape around the dome. Firmly press the two layers together to ensure they stick, then trim the excess pastry, leaving a 1-inch border around the dome. Brush the whole surface with egg wash.
Use the remaining pastry to cut decorative strips to adorn the sides. Lastly, cut three pastry circles of descending size and layer them on top to create a lid. Brush the pastry decorations with egg wash. Bake for 30 minutes or until deeply golden. Remove from the oven and allow to cool slightly.
Carve and serve the whole Vol au Vent tableside. Yes, it will be messy, but that’s part of the fun. Finish with shaved truffle, if using.
Note: Bake the pastry in the morning to save precious oven time Prepare the sauce up to 3 hours ahead and reserve at room temperature.
Note: if baking the pastry in advance, remove the lid and lining soon after baking. Store the pastry at room temperature; no need to re-heat before serving.