Slice the onion thinly and separate the shimeji mushrooms by hand.

Heat 1 tsp of salad oil in a frying pan over medium heat. Add the salmon fillet and cook until browned on one side. Flip and cook for another 2–3 minutes until fully cooked. Remove and let cool. Debone and remove skin, then flake the salmon.

In the same pan, add butter and heat over medium heat. Add the sliced onion and shimeji mushrooms, cooking until softened.

Add the flaked salmon, corn, miso, and sesame seeds to the pan. Stir to combine and let the mixture cool.

Place the cooled filling onto spring roll wrappers. Roll tightly and seal the edges with a mixture of flour and water. Repeat for all wrappers.