I’m not a fan of cooking chicken sous vide, as it renders the meat mushy if done too long. But what it does to fish, especially salmon, is nothing short of miraculous! The flesh melts on the tongue, like the Kobe beef of sea creatures. I like to cook my entrée-size salmon filets at 125°F for 8 minutes, but if you don’t have sous vide equipment at home, you can approximate the same method by submerging the fish in boiled, salted water (which you have already prepared to cook the soba) and letting it sit at room temperature while you cook the rest of the meal.
The water will immediately cool from 212° closer to the 125° range, and while the salmon won’t be quite as silky, it will come out perfectly rare inside, and you can just leave it, as the water will cool before the fish gets overcooked. Purists might balk at the water method, as some of the salmon flavor will be lost — but this is home cooking. And they can’t see what you’re doing, nor do they get to taste the delicious results.
Bring a small pot of water to a boil and season liberally with salt (it should taste like seawater).
Season the salmon with salt and pepper and place in a small bowl. Ladle some of the boiling water over the top until the salmon is fully submerged and allow to sit at room temperature. If the salmon is particularly thick, or if you like it more cooked, you can add another ladle of boiling water after 10 minutes. This should yield salmon that is soft, yet on the rare side.
Cook the soba per the package instructions, stirring after adding the noodles, then drain and rinse under cold running water. Drain well, and place in a bowl with the remaining ingredients, minus the salmon roe. Taste and adjust seasonings.
Remove the salmon from the water and pat dry. Top the noodles with the salmon and the roe. Eat immediately, as soba loses its bite as it sits.