Potato Rosti, Leek and Potato Veloute

STEP 1: RESERVE THE PEELINGS

Peel the floury potatoes over a bowl and keep every scrap of peel in cold water. The peelings are not a by-product here: they become the crisps and the crumble that finish the plate.

STEP 2: MAKE THE CIDER VINEGAR JELLY

Whisk the cider vinegar, water, caster sugar and agar agar together cold in a small pan. Bring to a full rolling boil and hold it there for one minute, or the agar will not set. Pour into a lined tray to a depth of about 5 mm and refrigerate until firm, then cut into 5 mm dice.

STEP 3: QUICK-PICKLE THE ONION

Warm the cider vinegar, water and caster sugar with a pinch of fine sea salt until dissolved. Pour over the onion rings and leave to cool. They are ready in 30 minutes and better after two hours.

STEP 4: MAKE THE LEEK OIL AND SEAWEED VINAIGRETTE

Blanch the leek green tops for 10 seconds, refresh in iced water and squeeze them bone dry. Blend with the grapeseed oil for a full minute, then strain through a fine sieve into a squeeze bottle. Stir the dried dulse or nori flakes, the cider vinegar and a pinch of fine sea salt into a small portion of the oil to make the dressing for the pearls. It should be sharper than a conventional vinaigrette, deliberately.

STEP 5: PAR-COOK AND CHILL THE ROSTI POTATO

Simmer the peeled floury potatoes whole in salted water for 12 to 14 minutes, until a knife enters the outer centimetre easily but meets resistance at the core. Drain, cool, then refrigerate for at least two hours or overnight. This is the step that gives you discrete strands rather than paste.

STEP 6: BUILD THE ROSTI

Coarse-grate the chilled potato and the raw beetroot, then squeeze the gratings firmly in a clean cloth to draw out excess water. Sweat the sliced onion in the cold-pressed rapeseed oil over low heat for 8 minutes until soft and sweet, and cool. Combine all three, season with the fine sea salt and black pepper at the moment of forming, and press firmly into the plating rings. The proportions of beetroot, onion and potato are unchanged from the plate as served.

STEP 7: CRUST THE ROSTI, DO NOT DEEP-FRY IT

Set the rings in a film of oil in a heavy shallow pan over medium heat and press down hard with a fish slice throughout the first three minutes, without moving them. Cook 6 to 7 minutes a side until a dark, brittle crust forms on both faces, then lift the rings away. A shallow-pan crust delivers the texture the plate was missing without the dominant fried flavour.

STEP 8: CONFIT THE POTATO PEARLS

Ball the waxy potatoes with the Parisienne scoop. Bring the rapeseed oil to 85C / 185F with the thyme, garlic and bay leaf and hold it there on a digital probe, not a degree higher. Add the pearls and start checking from six minutes. Pull them the moment a cocktail stick meets a whisper of resistance and lift them straight out of the oil. Undercooked is recoverable; overcooked is not.

STEP 9: MAKE THE VELOUTE BASE

Sweat the sliced leeks in the rapeseed oil over low heat for 12 to 15 minutes with a pinch of salt, until soft, sweet and barely coloured. Simmer the sliced floury potato separately in a little of the vegetable stock until tender, then combine it with the leeks and the remaining stock and simmer 5 minutes more.

STEP 10: BLEND SHORT, PASS FINE, KEEP IT THIN

Blend in bursts of 10 seconds at moderate speed only, until smooth. Never blend longer and never in a high-speed jug blender, which ruptures the potato starch and turns the liquid to paste. Pass through a fine chinois, pressing lightly. Stir in the oat cream and season with sea salt and white pepper. It should barely veil a spoon; if it coats the back of one, let it down with more stock.

STEP 11: ROAST THE PEEL CRISPS AND CRUMBLE

Pat the reserved peelings absolutely dry, toss with the rapeseed oil and roast at 190C / 375F for 12 to 16 minutes until dark and brittle. Season with flaky sea salt after roasting rather than before, and cool uncovered. Keep half whole as crisps, and crush the other half with the toasted nori sheet and the toasted buckwheat groats to a coarse crumble.

STEP 12: AERATE THE VELOUTE TO ORDER

Warm the veloute to around 60C / 140F without boiling, whisk in the soy lecithin powder until fully dispersed, then tilt the pan and run a stick blender at the surface until a stable foam builds. Skim the foam off the top and use it immediately, as it holds for a minute or two at most.

STEP 13: PLATE

Set a rosti in each warmed bowl. Dress the confit pearls in the seaweed vinaigrette and arrange them over and around it. Scatter the vinegar jelly dice and a few pickled onion rings down among the pearls where a fork will find them, rather than as a garnish on top. Spoon the crumble around the base as well as over it. Pour the veloute at the table, then crown with the aerated foam, the peel crisps standing upright, and a little flaky sea salt.