For the mushroom stock, dry the sliced mushrooms in a very low oven overnight. Fry the shallots and garlic gently in a little sunflower oil until translucent and then add the thyme and dried mushrooms.
Pour in the madeira and cook until reduced in volume by two thirds. Add 1.5 litres/2½ pints water and simmer for 2 hours, checking that it doesn’t boil dry. Remove from heat and leave to cool to room temperature. Put in the fridge overnight to mature. Next morning pass the stock through a sieve and heat to reduce by half and seasoning with salt and pepper.
To prepare the fermented mushroom juice, freeze the sliced mushrooms then mix them with the salt and leave in a warm place for 24 hours.
For the cabbage, trim and cut the cabbage in half. Boil 2 litres/3½ pints water with the salt to dissolve, let it cool and add the dill. Brine the cabbage in the liquid for 20 minutes, remove and pat dry.
For the mustard emulsion, in a food processor, blend together the eggs, vinegar, salt and mustard and add the oil until a thick emulsion is formed and pour into a heatproof cream whipper. Charge with two bulbs and hold in a bath at 50C.
For the mock teriyaki, gently simmer the stout vinegar until reduced in volume by two thirds. In a separate pan simmer the mead to evaporate away the alcohol then take off the heat. Add the mushroom stock, sugar and fermented mushroom juice and reduce slightly. Whilst constantly stirring, add the kuzu paste bit by bit to thicken. Add the reduced vinegar.
Preheat the oven to 180C/160C Fan/Gas 4. In an ovenproof frying pan, cook the cabbage halves in a little rapeseed oil and butter and then transfer the pan to the oven for 5-6 minutes. Place on a cloth to drain when cooked.
Meanwhile, fry the prepared wild mushrooms and baby onions in butter, wilt over the various garlic leaves, season and drain on a cloth.
Spoon a pool of the mock teriyaki sauce in a bowl and place the cabbage steak in the centre.
Scatter over the mushroom mixture, squirt some mustard emulsion on top and finish with some grated truffle and rapeseed oil.
