Truffled Potato Dumpling

STEP 1: THE DAY BEFORE - PICKLES, COAL OIL, ONION ASH AND CASHEW SOAK

Bring the verjus, water, caster sugar and salt to a simmer, stirring until the sugar dissolves, then take off the heat and cool. Pour half over the onion petals and half over the reserved beetroot stems in clean jars. Leave at least 4 hours, ideally overnight - this acidity is the backbone of the plate and it cannot be rushed. Char the leek tops or halved onions over a flame or under a hot broiler until genuinely black, not merely colored. Warm the neutral oil to 140F (60C), break the blackened alliums into it, hold at that temperature for 2 hours, then leave overnight and strain. This is coal oil, and the burnt note is the point. Spread the onion skins and trimmings on a baking sheet and blacken in a hot oven until brittle and carbon-black, then cool and grind to a fine powder. Cover the raw cashews with cold water and leave to soak overnight.

STEP 2: BLEND THE CASHEW CREAM

Drain the soaked cashews. Blend with the cold water at full speed for a full 4 minutes, scraping down twice. The blender jug should be warm to the touch and the mixture should look like pouring cream, not like a paste. Add the verjus, sherry vinegar, olive oil and salt and blend for another minute. Pass through a fine-mesh sieve or chinois, pushing hard with a ladle, and discard anything that will not go through - this pass is what removes the heavy, clinging body. Check the fall: a spoonful lifted and returned should ribbon and then flatten within a couple of seconds. If it holds a peak, loosen with verjus first and water second, never water alone. For the dark version, blend in the activated charcoal powder at the end and taste again for acidity, which charcoal flattens. Set aside 60 g / 1/4 cup for the filling and chill the rest.

STEP 3: MIX THE COAL OIL AND SHERRY VINAIGRETTE

Whisk the coal oil into the sherry vinegar, Dijon mustard and a good pinch of salt. Make more than you think you need. This dressing goes on the beetroots and again on the plate itself, and it is what carries acidity through the richness of the cashew cream.

STEP 4: MAKE THE WALNUT KETCHUP AND BLACK TRUFFLE PUREE

Blend the pickled walnuts with their liquor to a thick, spoonable ketchup, loosening with a little water if it stiffens on standing. Separately, blend the boiled potato with the black truffle paste, neutral oil and a splash of water to a glossy, pipeable puree. Season both, then transfer to squeeze bottles or small piping bags.

STEP 5: DRY AND FRY THE POTATO TUILE

Whisk the potato starch into the water in a small pan and bring to a simmer, stirring constantly, until it becomes a thick translucent gel. Beat in the onion ash and a good pinch of salt. Spread very thinly on a lined baking sheet and dry in the oven at its lowest setting, around 160F (70C), for about 3 hours until brittle and glassy. Break into shards. Heat the frying oil to 375F (190C) and fry the shards for a few seconds each, until they puff and shatter. Drain and salt. They should taste distinctly of burnt onion - a crisp that tastes of nothing is the fault this step exists to fix.

STEP 6: ROAST AND DRESS THE BABY BEETROOTS

Heat the oven to 350F (180C). Toss the baby beetroots with olive oil and salt, add the lemon rind, thyme, bay leaves and halved garlic bulb, wrap tightly in foil and roast for 45-60 minutes, until a knife slides through with no resistance. While they are still warm, rub off the skins and halve any that are larger than a walnut. Dress them generously in the vinaigrette while warm, so they drink it up.

STEP 7: COOK THE TRUFFLED GIROLLE FILLING

Sweat the shallots and garlic in the olive oil over a low heat, without color, for about 8 minutes. Raise the heat, add the girolles and cook hard for 6-8 minutes, until every drop of water they release has gone and they begin to catch and squeak against the pan. Add the thyme leaves and season. Off the heat, fold through the chopped fresh truffle and the reserved cashew cream. Cool completely, then roll into 12 balls of about 20 g / 3/4 oz each and freeze for 30 minutes. Frozen centers are what stop the filling bursting the dough.

STEP 8: BAKE AND RICE THE POTATOES

Bake the whole unpeeled potatoes at 400F (200C) for about an hour, until collapsing. Halve them and pass the hot flesh through a potato ricer onto a tray - never a food processor, whose blades work the starch into glue. Spread it out and let the heat escape for 2 minutes. This is the step that keeps the interior fluffy rather than dense.

STEP 9: SHAPE AND STEAM THE DUMPLINGS

While the riced potato is still warm, scatter over the potato starch, semolina flour and salt (and the activated charcoal powder, for the dark version) and bring together with the lightest possible hand. Work it as little as you can; a kneaded dough goes rubbery, and the casing is meant to be fluffy. Divide into 12 pieces of about 48 g / 1 3/4 oz. Flatten each piece, sit a frozen filling ball in the center, close the dough around it and roll smooth. Dust lightly with semolina. Steam for 9-10 minutes, until the surface turns matte and a dumpling feels light in the hand.

STEP 10: PLATE AND SERVE

Warm four plates. Spoon the cashew cream across each and spread it flat with the back of the spoon. Arrange the dressed beetroots, pickled onion petals and pickled beetroot stems around, with small dots of walnut ketchup and black truffle puree between them. Spoon more vinaigrette over the plate itself, not only over the beetroots. Only now, pan-fry the steamed dumplings in a little neutral oil in a hot skillet, on one side only, until that side is deeply golden and crisp. Sit three on each plate, crisp side up. Shave the fresh truffle over, crown each dumpling with a shard of tuile, and finish with edible flowers and soft herbs, or charred spring onions for the dark version. For the full table theater, cover with a cloche, fill it with cold smoke from a smoking gun and release it in front of your guests.