Mushroom and Walnut Pâté en Croûte

Make the pastry: combine flour and salt in a bowl and make a well in the centre. Heat butter, milk and water in a small saucepan over medium heat until the butter melts and the liquid just begins to simmer. Pour the hot liquid into the flour and stir rapidly with a wooden spoon until a shaggy dough forms. Turn onto a lightly floured surface and knead briefly for 1 minute until smooth and pliable. Wrap tightly and set aside — do not refrigerate; the dough must remain warm and workable.

Prepare the farce: beat cream cheese, eggs, double cream, Dijon mustard and Gruyère together in a bowl until completely smooth. Season lightly with salt and pepper. Cover and refrigerate until needed.

Melt 2 tbsp butter in a large wide skillet over high heat until foaming. Add the shallots and garlic and cook, stirring, for 2 minutes until softened and translucent.

Add all three mushrooms to the pan and spread into a single layer. Cook over high heat, without stirring, for 4 minutes until the mushrooms release their liquid and it evaporates from the pan.

Continue cooking, stirring occasionally, for a further 6–8 minutes until the mushrooms are deeply golden and completely dry — the mixture should hold together and not steam.

Add the cognac and stir constantly for 1 minute until the alcohol is fully evaporated.

Stir in the thyme, rosemary, salt, pepper and nutmeg. Remove from heat and stir in the walnuts and parsley. Spread onto a baking tray and allow to cool completely to room temperature — approximately 30 minutes.

Preheat the oven to 200°C, or 180°C for a fan oven, or gas mark 6. Lightly grease a 20 cm × 9 cm loaf tin.

Divide the warm pastry into two-thirds and one-third. Roll the larger portion on a lightly floured surface into a rectangle large enough to line the base and sides of the loaf tin with a 1 cm overhang. Press gently into the tin, ensuring no air pockets at the corners.

Spoon half the cooled mushroom and walnut mixture into the pastry-lined tin and press into an even, compact layer. Pour half the farce over the mushroom layer and spread evenly. Add the remaining mushroom mixture, then pour and spread the remaining farce on top, smoothing the surface level with the tin.

Roll the remaining pastry into a rectangle to fit the top of the loaf as a lid. Lay it over the filling and press the edges together firmly, crimping to seal. Trim any excess with a sharp knife. Cut two small chimneys — 1 cm diameter — in the pastry lid and insert small rolls of foil or pastry tubes to keep them open during baking. Brush the surface evenly with egg wash.

Bake at 200°C for 20 minutes until the pastry sets and turns pale gold.

Reduce the oven temperature to 170°C, or 150°C for a fan oven, or gas mark 3 and bake for a further 60–70 minutes until the pastry is a deep, even golden brown and a digital thermometer inserted through a chimney into the centre of the filling reads 72°C.

Remove from the oven and leave to cool in the tin for 1 hour, then refrigerate uncovered for a minimum of 12 hours and up to 24 hours — this resting period is essential for the filling to set firm enough to slice cleanly.

If using the aspic: combine the strained porcini liquid and agar-agar in a small saucepan, bring to a full boil over medium heat, and stir for 2 minutes until the agar is completely dissolved. Remove from heat, stir in the dry sherry and adjust seasoning.

Allow the aspic to cool to room temperature — approximately 10 minutes — until it is liquid but no longer steaming. Using a small funnel or piping bag, pour slowly through the pastry chimneys in several increments, pausing between each pour to allow the liquid to settle into any gaps. Refrigerate for a further 2 hours until the aspic is fully set.

To serve, unmould carefully, slice with a sharp serrated knife, and allow slices to come to room temperature for 20 minutes before plating.