Step 1Wipe the surface of the kombu with a moist towel to clean.
Step 2In a medium saucepan, combine the kombu with 7 3/4 cups water and over very low heat, allow the kombu to soften as it soaks in the water. Slowly raise the temperature of the water over medium heat so a thermometer inserted reads 140 degrees. Maintain the temperature for one hour. While the kombu is steeping, place the bonito flakes in a medium-size bowl.
Step 3Remove the kombu from the broth, increase the heat to medium-high until a thermometer reads 176 degrees. Turn off the heat and immediately pour the broth over the bonito flakes into the bowl.
Step 4Let the bonito flakes sit in the broth, thoroughly soaked, for 10 seconds. Strain the liquid through a cheesecloth-lined fine-mesh strainer. Let the liquid drain naturally, without pressing down on the solids. Discard the solids and store the dashi in the refrigerator for up to one week. Makes about 5 cups dashi stock.
Step 1In a small bowl, combine light soy sauce, mirin and egg white. Set aside.
Step 2Chop two-thirds of the shrimp into half-inch pieces. Coat with the regular soy sauce. Set aside.
Step 3In a food processor, combine the remaining shrimp, chopped fish fillet, grated yam, kombu dashi and dissolved kuzu with the egg white mixture. Pulse to puree.
Step 4In a medium bowl, combine the ground shrimp mixture with the chopped shrimp. Shape into six equal balls and sprinkle with black sesame seeds evenly just over the top of each. If the mixture sticks to your hands while forming the balls, grease your hands with a little vegetable oil.
Step 5Pour vegetable oil to a height of 3 inches into a medium saucepan. Heat the oil until a thermometer inserted reads 325 degrees. Deep-fry the shrimp balls for about 3 minutes until golden brown. Drain on a rack and reserve in a warm place.
Step 1Slice 12 slices of the daikon as thinly as possible using a mandoline or knife. Cut the slices to resemble cherry tree petals, and reserve in a small cup of water.
Step 2In a large saucepan, bring 8 cups of water to a boil. Add baking soda and peas and blanch for 7 to 8 minutes. Drain the peas and put them in a bowl of ice water. Strain the cooled peas and push them through a fine-mesh strainer to remove the second skin.
Step 3In a food processor or using an immersion blender, fully puree the strained peas with the dashi stock.
Step 4Combine the pea puree, soy sauce and salt in a small saucepan over medium-high heat and gently bring to a boil, carefully stirring so the soup does not burn on the bottom and heats evenly. Stir in the kuzu slurry, or enough to thicken the soup. Season with one-eighth teaspoon salt or to taste. (Makes a little over 1 1/2 cups soup.)
Step 5In each of six small serving bowls, place 1 shrimp ball. Cover with about one-fourth cup soup and garnish with two petal-shaped pieces of daikon. Serve immediately.