Steps

1. Dice 1/2 onion into 1cm cubes. Cut 1 potato into 2cm cubes.
   🕒 01:11
2. Place 150g of frozen seafood mix in a bowl, coat with 2 tbsp of potato starch for de-odorizing, add a small amount of water, and mix well. Rinse several times under running water and drain. (This is the trick!) Washing with potato starch thoroughly removes surface dirt and odors.
   🕒 02:11
3. Melt 20g of butter in a frying pan over medium heat. Add the onion and sauté until softened.
   🕒 03:01
4. Add the potato and stir-fry briefly to coat everything.
   🕒 03:44
5. Add the drained seafood mix, sprinkle 1.5 tbsp of all-purpose flour over it, and stir until the flour is no longer visible.
   🕒 03:59
6. Add 2 tbsp of cooking sake (rice wine) to remove the seafood's odor and enhance its flavor.
   🕒 04:27
7. Tear and add 1 small pack of maitake mushrooms and stir-fry briefly.
   🕒 04:40
8. Pour in 2 cups of milk all at once and bring to a simmer while stirring.
   🕒 05:02
9. Once simmering, add 50g of macaroni and salt to taste. Cover and simmer until the macaroni is tender. (This is the trick!) The starch from the potatoes and the flour from the macaroni will naturally thicken the sauce.
   🕒 05:23
10. Stir occasionally to prevent sticking.
    🕒 06:10
11. When the macaroni is tender and the sauce has thickened, increase the heat slightly and reduce the liquid until the bottom of the pan is visible when you draw a line with a spoon. This is your guideline.
    🕒 06:50
12. Taste and adjust seasoning with salt to taste and pepper to taste.
    🕒 07:44
13. Transfer the gratin to an oven-safe dish.
    🕒 07:59
14. Mix pizza cheese to taste throughout the gratin. (This is the trick!) Mixing in the cheese creates a cohesive texture and makes it stringy when you eat it.
    🕒 08:27
15. Sprinkle the remaining pizza cheese to taste over the surface of the gratin.
    🕒 08:56
16. Bake in a toaster oven until the surface is golden brown.
    🕒 09:04