To make tempura sauce, combine dashi, soy sauce, mirin, and sugar in a small saucepan and bring it to a boil. Then lower the heat and let it simmer until sugar is completely dissolved. Remove from heat and set aside.
To prepare shrimp, read step-by-step instructions with pictures on How To Prepare Shrimp for Shrimp Tempura to make shrimp straight
In a deep fryer, heat 1½" (3 cm) of the oil to 338-356F (170-180C). You can check the temperature with chopsticks or with a thermometer. When you see small bubbles around chopsticks, it’s pretty much ready for deep frying
To make tempura batter, sift the flour into a large bowl.
Add the egg into very cold water.
Whisk the egg mixture vigorously and discard the form on the surface.
As you slowly pour the egg mixture into the flour, mix the batter but do not over mix. It's okay to leave some lumps in batter. Keep the batter cold all the time.
Dust corn starch on top of shrimps.
Coat the shrimp in batter.
Deep fry until golden brown, about 1½ minutes. Do not crowd the fryer with shrimps; leave at least half of oil surface empty. Don't over cook the shrimp as they becomet tough texture. Transfer cooked shrimp tempura to a wired rack or a plate lined with a paper towel to drain excess oil. Between batches, remove the crumbs which will burn and turn the oil darker if left in fryer.