Slice the onion thinly. Cut the carrot in half lengthwise and slice into thin half-moons. Chop the Hayashi roux.

In a microwave-safe container, combine onion, carrot, chicken mince, Hayashi roux, salt, pepper, and water. Cover loosely with plastic wrap and microwave at 600W for 5 minutes. Stir to distribute the seasoning evenly, cover again, and microwave for another 3 minutes until fully cooked.