Begin by preparing the wild garlic oil. Carefully rinse the wild garlic, then blanch for 30 seconds in a pan of salted boiling water. Drain and plunge the leaves into iced water. Once cold, pat dry thoroughly.
Chop the wild garlic roughly, add to a blender and pour in the oil. Blitz briefly on a low speed, then increase in speed for 30 seconds until the oil is a bright, vibrant green colour.
Pass through a fine sieve. Transfer to a suitable container and store in the fridge until required.
Take the dashi and pour into a pan, reduce by half, set to one side.
To make the emulsion, whisk together the egg yolks, mustard and vinegar in a bowl until smooth. Weigh out 200ml of the wild garlic oil and add this to the bowl in a slow steady stream, whisking continuously, until the mixture has emulsified to form a green mayonnaise. The consistency should be that of single cream so you will most likely need to add a little of the reduced dashi stock to loosen it. Season to taste. Take 30ml of the remaining garlic oil to make the wild garlic dressing, add 1 teaspoon of yuzu and taste, if you feel it needs more acidity add a little more yuzu, pour into a jam jar and set to one side.
Sprinkle a little fine sea salt on each piece of cod and leave for 7 minutes. Rinse and pat dry thoroughly.
Heat a cast iron frying pan to high and a little oil and a knob of butter. Place the fish in the hot pan, after a minute or so add a tablespoon of reduced dashi stock to each piece of fish, keeping the heat to high, once the stock has evaporated reduce the heat slightly. When the fish is three quarters cooked flip it over, cook for a little longer then turn the heat off. In the meantime boil or steam the asparagus and have 4 warm plates ready. Place the vegetables on the plate, arrange the cod on top. Swirl a little of the wild garlic emulsion around the plate and give the dressing a good shake before drizzling the dressing around the plate. Serve with new potatoes.