Grate the turnip and lightly squeeze out excess water. Cut the root off the shimeji mushrooms and separate them into bite-sized pieces.

Remove the vein from the shrimp, sprinkle with sake, let sit for 5 minutes, and pat dry.

In a microwave-safe container, mix all sauce ingredients. Cover loosely with plastic wrap and microwave at 600W for 3 minutes. Stir, cover again, and microwave for another 2 minutes until thickened.

Place hanpen in a plastic bag and knead until smooth.

In a bowl, mix grated turnip, hanpen, egg white, potato starch, and salt until combined.

Line a microwave-safe container with plastic wrap. Add 1/4 of the turnip mixture, 3 shrimp, and another 1/4 of the mixture. Wrap tightly. Repeat for the second portion. Microwave at 600W for 3 minutes until set.