Bluestem'S Chawanmushi With Hon Shimeji, Scallion, And Dashi

Rinse the kombu under cold water. In a medium saucepan, bring the kombu and water to a boil over high heat. Turn off the heat. Remove the kombu and add the bonito flakes. Set aside to steep. The bonito will become pulpy and slowly sink. When all of the bonito has settled below the water line, strain the dashi broth through a fine-mesh sieve, discarding the bonito.
Combine the dashi with the soy sauce, vinegar, and mirin in a medium saucepan. Bring it to a low simmer over medium heat. Turn off the heat and keep the broth warm.
Heat the sesame oil in a small saute pan over medium heat. Add the mushrooms, water, and mirin and saute lightly for about 30 seconds to slightly soften the mushrooms. Remove the mushrooms from the pan.
Preheat the oven to 275u0b0F. In a blender, mix the dashi, soy sauce, mirin, vinegar, and eggs on low speed. Strain the base through a fine-mesh sieve. Divide the chawanmushi base evenly among 4 small bowls. Cover the bowls tightly with plastic wrap.
Place the bowls in a casserole dish with 1 inch of water. Put the casserole dish with the bowls of chawanmushi in the oven and bake the bowls for about 40 minutes, until the chawanmushi is just set but still a little jiggly in the middle. Let the bowls cool slightly and carefully unwrap them, being careful of the escaping steam. To serve: Pour 1/8 cup of the chawanmushi broth over each custard. Top with some sauteed mushrooms and sliced scallions as a garnish. Serve immediately.