Grate ginger and chop half of the Negi into small rounds.
To make seasonings, combine 3 Tbsp mirin, 3 Tbsp sake, and 1 Tbsp soy sauce.
Add 2 Tbsp water and 2 tsp potato starch/cornstarch. Mix all together until everything is combined well.
Heat a saucepan or frying pan over medium heat. When it’s hot, add 1 Tbsp sesame oil and chopped negi. Coat the negi with oil until fragrant.
Add the ground meat and break up the meat.
Add the grated ginger and cook the meat until no longer pink.
Add the miso and sugar and combine well.
Add the seasonings and cook on medium-low heat.
When the cooking liquid is reduced to your liking, turn off the heat. You can leave more sauce or less sauce depending on how you want to use the meat sauce. Transfer to a bowl or container. Serve hot along with steamed rice, lettuce cups, etc (See the post for some ideas).
You can keep in the refrigerator for up to one week. Reheat only the portion you will serve. You can also freeze it up to 3-4 weeks.