Lay salmon flat in a chopping board. Remove all the pin bones using a plier, pulling it out at an angle. Next, remove the skin from the salmon using a sharp knife. Slice into small cubes.
Combine all the teriyaki sauce ingredients in a bowl. Stir until sugar has dissolved. Taste and adjust sugar/ vinegar/ soy sauce based on preference.
Melt butter in a nonstick skillet or wok over medium heat. Add the salmon pieces and drizzle with a couple of teaspoons teriyaki sauce. Gently toss until fish is half-cooked.
Add corn kernels and half of the scallions. Continue cooking for 1 to 2 minutes. Add the cooked rice and pour the remaining teriyaki sauce. Toss everything together and cook until liquid evaporates.
Shove rice to the side of the wok / skillet. Add 1/2 tbsp oil into the cleared space move wok so the heat is centred over the cleared space. Pour in egg, cook it through properly, don't "soft scramble".
Stir the egg into the rice. Add mung bean sprouts and remaining scallions. Toss again for another minute. Remove from heat and serve immediately!
Notes
If using canned salmon - use canned salmon with a neutral flavor (e.g. with water or oil). Don’t use salmon with mayonnaise or other strong flavors.
Rice - use day-old or freshly cooked. If using freshly cooked rice: cook it as you normally do but with a little less water than usual i.e. reduce up to 1/2 cup of water. This will prevent the rice from being too starchy. Once the rice is done, spread it onto a plate so it will cool off faster. Then transfer the rice into the fridge and let it sit there until you’re ready to cook.
Make it kid-friendly - omit mirin (which contains alcohol) and add a little bit more sugar to the sauce to compensate for the sweetness.
Sugar can be substituted with honey. Start with 1 tbsp for every 2 tbsp soy sauce and adjust from there.
Other recommended vegetables: green peas, shredded lettuce or napa cabbage, carrots, and broccoli. If using other hard vegetables like broccoli and carrots slice into small bits and stir-fry BEFORE the salmon until partially cooked.
Cooking tip: TOSS instead of STIR to keep the shape of the salmon.