Cut the onion and burdock root into thin, uniform strips. Slice the leek thinly on a diagonal. Combine with the dried sakura shrimp, then lightly dust everything with about 2 tablespoons of extra all-purpose flour (not from the main ingredient list).

Beat the egg into the cold water.

Microwave the all-purpose flour for 2 1/2 minutes at 500W. Mix the flour and the egg mixture together in a 1:1 ratio, whisking lightly.

Prepare each tempura individually. Take a portion of the mixed vegetables and shrimp, place in a separate bowl, and coat with 1 tablespoon of batter. Gently shape and place into oil heated to 350°F (180°C).

If the mixture starts to fall apart, drizzle another tablespoon of batter over the top to help it hold together. Do not touch; once it firms up, turn it over.

When golden brown, remove and place on a wire rack.

Do not place on paper towels—use a wire rack instead. Paper towels can cause the tempura to reabsorb oil and become soggy.