Step 1: Prepare the Salmon variety of fillings
If you have leftover salmon, flake it into small pieces using a fork and a small bowl of water.
In a small bowl, combine the flaked salmon with 1 tablespoon of Kewpie mayo (a Japanese-style mayonnaise) and 1 tablespoon of sriracha sauce. Adjust the sriracha to your preferred level of spiciness. Mix well until the ingredients are evenly combined.
Step 2: Season the Rice
Take your leftover cooked jasmine rice and place it in a microwavable large bowl.
Heat up your rice in the microwave for 1 minute or until it is warmed and soft.
Add 2 tablespoon of mirin and 2 tablespoon of rice vinegar - adjust the taste to your liking.
Step 3: Shape the Onigiri (BY HAND)
Wet your hands with a small bowl of water to prevent the rice from sticking. Take a handful of seasoned rice and place it in your palm.
Flatten the warm rice in your hand and create a small well in the center for the salmon filling.
Add a spoonful of the creamy salmon mixture into the well.
Encase the filling with the rice and shape it into a triangle shape or oval triangular shape, whichever you prefer. Press the rice gently to ensure it holds its shape using an onigiri mold.
Shape the Onigiri (BY MOLD)
Place seasoned rice in the mold, filling it halfway, and create a slight hollow for your chosen fillings.
Spoon your desired filling into the hollow, then top with more rice to fill the mold completely.
Seal with the lid, and press down firmly. Uncover, invert the mold, and press the bottom button to release your onigiri.
Step 4: Pan fry and wrap with nori
Brush the onigiri with a little bit of sesame oil. Pan-fry the onigiri until it becomes slightly crispy and the rice develops a golden-brown crust. Place them on a baking sheet lined with parchment paper.
Take nori strips (nori seaweed) and wrap them around the onigiri. The nori strips will not only add a different flavor but also make it easier to hold and eat.
Step 5: Garnish (Optional)
If desired, sprinkle some black sesame seeds, white sesame seeds, or toasted sesame seeds over the top of your onigiri for extra flavor and texture.