How to Make It
In a small bowl, dissolve the dashi powder in the water. In a heatproof bowl, whisk the egg yolks with the miso, sugar, mustard, soy sauce and dashi broth. Set up an ice bath nearby. Set the bowl over a pan of barely simmering water, making sure that the bowl is not touching the water. Whisk constantly until the sauce is slightly thickened and reaches 160°, about 3 minutes. Immediately set the bowl in the ice bath to stop the cooking and whisk the sauce until cool. Whisk in the rice vinegar and refrigerate the miso vinaigrette until chilled.
In a large pot of boiling water, cook the lobsters until they turn bright red, about 8 minutes. Drain and let cool.
Twist the bodies from the tails. Using scissors, cut along the underside of the tails and remove the meat. Halve the tails lengthwise and discard the dark intestinal veins. Crack the claws and legs and remove the meat. Cut all of the lobster into 1-inch pieces, transfer to a bowl and refrigerate until chilled.
Bring a pot of salted water to a boil. Set up an ice bath nearby. Blanch the asparagus in the boiling water for I minute. Using tongs, transfer the asparagus to the ice bath to cool, then drain and blot dry. Transfer the asparagus to a small baking dish.
In a small bowl, whisk the soy sauce with the lemon juice, lime juice and peanut and sesame oils. Drizzle over the asparagus and toss gently to coat.
Add 1/4 cup of the miso vinaigrette to the lobster and toss to coat. Set the toasts on plates. Top with several spears of asparagus and a scoop of lobster and garnish with radish slices. Sprinkle with scallions and sesame seeds and serve, passing the remaining miso vinaigrette at the table.
Dashi powder is available at many health food stores and at Asian markets.