Add <quantity>⅔<unit>cup</unit></quantity> of rice wine vinegar to a saucepan over high heat

Combine <quantity>½<unit>cup</unit></quantity> of sugar with a pinch of salt and add to the saucepan. Stir to dissolve

Add a <quantity>5<unit>cm</unit></quantity> x <quantity>5<unit>cm</unit></quantity> kombu leaf

Add the juice of <quantity>½</quantity> a lemon

Bring it to a boil and stir until no grains of sugar are visible. Turn off the heat

Transfer the liquid to a container. Remove the kombu leaf and let it cool down

Trim, halve, and peel <quantity>2</quantity> large shallots

Separate the inner parts and reserve for another recipe. Thinly slice and cut the outer layers into a very small dice

Transfer the shallots to the liquid and let them sit for at least 10m to pickle. The pickled shallots are ready. Store them in the refrigerator in the liquid

Add <quantity>2</quantity> egg yolks to a tall container

Add <quantity>1<unit>tsp</unit></quantity> of white miso

Blend with a hand blender until smooth

Slowly add <quantity>¾<unit>cup</unit></quantity> of vegetable oil, while blending, to emulsify

Add <quantity>1<unit>tbsp</unit></quantity> of rice wine vinegar and blend it to incorporate

Gradually add <quantity>3<unit>tbsp</unit></quantity> of toasted sesame oil, while blending, to thicken the mayo

Season with salt to taste and add <quantity>2<unit>tbsp</unit></quantity> of water. Blend until completely incorporated. The soy & sesame mayo is ready

Fill a piping bag with the mayonnaise

Add <quantity>7<unit>tbsp</unit></quantity> of soy sauce to a bowl

Add <quantity>5⅓<unit>tbsp</unit></quantity> of mirin

Add <quantity>3<unit>tsp</unit></quantity> of rice wine vinegar

Add <quantity>3<unit>tsp</unit></quantity> of water

Add <quantity>4<unit>tsp</unit></quantity> of yuzu juice

Stir to combine. The ponzu sauce is ready

Add <quantity>100<unit>g</unit></quantity> of trout roe to a small bowl and cover it with <quantity>3<unit>tbsp</unit></quantity> of the ponzu sauce

Mix to cover all the trout roe. The marinated trout roe is ready

Trim and slice <quantity>½</quantity> of a cabbage head

Place the cabbage in a sieve, generously add salt to taste, and knead to break the cells. Let it sit for 20m to drain water

Clean <quantity>2<unit>cups</unit></quantity> of mushrooms with a brush or a paper towel

Remove the harder stems and cut or tear the mushrooms into bite-size pieces

Place a pan over high heat and add <quantity>1<unit>tbsp</unit></quantity> of vegetable oil until it just barely smokes

Add the mushrooms

Season with salt and black pepper to taste

Stir fry for about 4m until all the liquids evaporate and the mushrooms brown

Add <quantity>2½<unit>tbsp</unit></quantity> of butter and reduce the heat to medium-low

Stir to coat all the mushrooms and fry for 5m until they are deep brown

Crack <quantity>2</quantity> eggs into a bowl

Add <quantity>150<unit>g</unit></quantity> of all-purpose flour to a large bowl. Add salt to taste

Turn the heat to low and let the mushrooms cook for 2m until crispy

Place the pan-fried mushrooms on a paper towel. Reserve the butter to sear the pancakes

Add <quantity>150<unit>ml</unit></quantity> of water to the flour while whisking

Add the eggs and whisk until smooth

Squeeze the cabbage to drain the remaining the water

Add the cabbage to the batter and mix

Coat the bottom of a frying pan over high heat with vegetable oil

Add <quantity>½<unit>cup</unit></quantity> of the batter to the frying pan and spread it over the bottom

Add the butter from the mushrooms and season with black pepper to taste. Fry for 5m until the bottom turns light brown

Thinly slice <quantity>6</quantity> spring onions

Flip the pancake and fry for another 5m or until light brown

Remove from the frying pan when crispy and golden brown. Cut in quarters. Repeat with the remaining batter

Place the okonomiyaki on a plate

Drizzle the soy & sesame mayo and the okonomiyaki sauce all over the pancake

Spread the mushrooms on top

Top with <quantity>4<unit>tsp</unit></quantity> of the marinated trout roe

Top with <quantity>4<unit>tsp</unit></quantity> of the pickled shallots

Add the sliced spring onions

Add katsuobushi to taste

Finish with sesame seeds, salt, and black pepper to taste. The okonomiyaki with mushrooms is ready

Enjoy it with a cold glass of beer!