Make the dipping sauce: Combine all ingredients in a bowl. Set aside to allow the flavors to develop.
Prepare the shrimp: Butterfly the shrimp by cutting down the back, being careful not to cut all the way through. Open the shrimp like a book and rinse well with cold water.
Make the Tempura batter: Put the flour in a bowl and whisk in the seltzer to get out all the lumps. Add the egg yolks and blend it in well. Flavor with sesame oil and a pinch of salt. The batter should be the consistency of heavy cream.
Time to fry: Heat about 2 inches of peanut oil to 375 degrees F in a wok or deep skillet. Dry the shrimp and vegetables well. Dust them with flour to soak up any remaining moisture and shake off the excess. Dip them into the batter one by one. Drop 4 or 5 pieces at a time in the hot oil, do not overcrowd the pan. Fry until golden brown, turning once, about 3 minutes. To keep the oil clean between batches, skim off the small bits of batter that float in the oil. Remove the fried shrimp and vegetables from the oil and drain on paper towels; season them with salt. Serve with the dipping sauce.