Slice the onion thinly. Cut the potatoes into 1cm thick sticks and soak them in water. Drain and microwave the potatoes in a heatproof container covered with plastic wrap for 2 minutes at 600W.

Mix the seasoning ingredients (sake, mirin, sugar, miso, and garlic) in a bowl.

Heat olive oil in a frying pan over medium heat. Add the ground meat and stir-fry until the meat changes color.

Add the potatoes and onion to the pan. Stir-fry until the potatoes are tender, then add the seasoning mixture and stir-fry until well combined.