First peel deveined shrimp leaving the tails on.
To straighten the shrimp: Turn the shrimp over its back side and make small slits where the feet used to be with a knife and snap the shrimp until you feel a break. The more slits the flatter the shrimp will be.
Then pat dry the shrimp with paper towel to remove excess moisture.
In a medium bowl, whisk together tempura batter ingredients until smooth and runny.
Then mix shrimp into the batter ensuring it's fully coated.
In a large heavy bottomed pan, heat vegetable oil or any neutral oil on medium high heat until you reach 350 degrees F with a digital instant read cooking thermometer. Or insert a wooden spoon into the hot oil and look for rapid bubbles. Lower battered shrimp into the hot oil away from you. Fry in small batches, about 3-4 pieces per batch.
Drizzle 2 teaspoon of excess batter on top of each piece of shrimp, flip it over and let this fry for 1 minute or until crispy. Then drizzle another 2 teaspoon of batter, flip over and fry for another 1 minute or until it's crispy.
Remove fried shrimp with tongs or a slotted spoon and transfer to a wire rack or paper towel baking sheet to allow excess oil to drip off. Repeat for the remaining shrimp.
In a small bowl, combine sauce ingredients together and serve with tempura.