Peel and boil the potato until soft all the way through.

Use a ricer or mash the potato until smooth.

Slowly fry the onion until translucent, then let it cool.

In a large bowl, add the ground beef, ground pork, ground turkey or chicken, mashed potato, cooked onion, egg, cornstarch, and milk.

Mix everything together well, then season to taste with salt and pepper.

Fry a small piece of the mixture to check the seasoning, and adjust if necessary.

Scoop the meat mixture using a cookie scoop, meatball tongs, or two spoons.

Place each scoop of meat on a lined sheet tray (lined with parchment or foil).

Roll each meatball in your hands to make it nice and round, using a bit of water on your hands to prevent sticking.

Bake at 190°C (375°F) for about 15 minutes or until cooked through.

Once baked, let the meatballs cool. You can store them in the refrigerator or the freezer.

Fry the meatballs in a bit of butter until brown on all sides.