Pour 2 tbsp Japanese soy sauce (koikuchi shoyu), 1 tbsp light brown sugar, ½ tbsp sake, ½ tbsp mirin and 3 tbsp dashi stock to a small pan. Bring it to a boil over medium, then reduce the heat and gently simmer for 3 minutes.
Remove the pan from the heat and leave to cool. Transfer to a small dipping bowl and add 1 tsp toasted sesame oil and 1 tsp ground sesame seeds. Mix well.
Divide 2 portions cooked Japanese short-grain rice into bowls and top with 200 g seafood of your choice.
Garnish with shiso leaves, nori or chopped green onion.
Pour the sauce into dipping bowls and serve alongside the donburi. Apply wasabi to each piece of fish as you eat, then dip it in the sauce and eat it with the rice. Enjoy!
Notes
Buy fish labeled sashimi grade or for sushi: This is the line you do not skip. If the label does not say it, the answer is no, even when the fish looks gorgeous. The fish needs to go through a special process to deem it safe to eat raw, so it's always better to be safe than sorry.Get the rice down to warm, not hot, before any fish: Steaming rice cooks the underside of the slices, and lean tuna akami goes firm and dry the instant it catches heat.Cool the tare completely before it touches the fish: Raw fish dipped in hot sauce cooks the edges and wilts them. Let the tare reach room temperature or cooler. Cold sauce on cold fish keeps the slices clean, not half-steamed.