Heat up a frying pan on a medium high heat. Once hot, add 1 tsp cooking oil and 100 g ground chicken and fry until browned.
Add 1 tbsp Japanese soy sauce (koikuchi shoyu), ½ tbsp mirin, 1 tsp sugar and 1 tsp sake to the pan and fry everything together. When the liquid has fully absorbed, remove from the heat.
Add 600 g cooked Japanese short-grain rice and the seasoned chicken to a large bowl and mix thoroughly. Once evenly distributed, I recommend dividing into equal portions to ensure all the onigiri are the same size.
Once your onigiri are shaped, wrap them with nori. Eat them straight away or put them in your lunch box with an ice pack.
Enjoy!
Notes
If you have leftovers, wrap each individual onigiri in plastic wrap without nori and place them in an airtight container in the freezer. (This prevents freezer burn.)
Best eaten within 1 month. Microwave to defrost and enjoy with fresh nori. Refrigeration is not recommended.
Choose between ground chicken thighs (more flavorful) or breasts (leaner). Ground turkey works well as an alternative.
For extra flavor, add minced ginger or garlic when frying the ground meat.