Step 1: Pat shrimp dry with paper towels and set aside.
Step 2: In a medium bowl, whisk together flour, cornstarch, baking powder, and salt.
Step 3: In another bowl, lightly beat the egg, then mix in ice-cold water.
Step 4: Gently combine wet and dry ingredients until just mixed; do not overmix.
Step 5: Heat 2 inches of vegetable oil in a deep pot to 350°F (175°C).
Step 6: Dip each shrimp in the batter, letting excess drip off, then fry for 2-3 minutes until golden and crispy.
Step 7: Drain tempura on a wire rack or paper towels.
Step 8: Mix soy sauce, rice vinegar, honey, and ginger for dipping sauce; sprinkle with sesame seeds.
Step 9: Serve immediately with dipping sauce.