Pour the soy sauce, honey, mirin and oil into a small bowl, add the chilli flakes and whisk until well combined.
Pour the marinade into a zip lock bag. Add the two salmon fillets.
Expell the air from the bag and seal.
Place the bag in the fridge for at least 2 hours, but overnight works well. (or if you wish to freeze, place the bag with the salmon and marinade straight into the freezer)
Make the mantou dough
as directed. But stop at step 6.
Divide the dough into 10 balls, flatten each ball with your hand to create an oval shape.
Cut 20 squares of cooking paper.
Carefully fold each oval in half (like a clam) with a sheet of paper between the dough envelope.
Place the folded bun onto a second sheet of paper.
Repeat for all the buns.
Place the buns into a steamer and allow to rise for 20 minutes.
Pour boiling water into your steamer and cook the buns for 15-20 minutes until puffed up and cooked through.
Meanwhile place the salmon into a dry frying pan and cook over a medium heat for 3 minutes a side (or until cooked to your liking). You can also bake the salmon for 8 minutes at 200ºC/180ºC fan forced/Gas mark 6.
Gently flake the salmon into large chunks
Thinly slice the cucumber, spring onion and shred the red cabbage.
When the buns are cooked allow them to cool enough to handle, then gently split them open and remove the paper inside.
Fill each bun with some cucumber, cabbage, salmon, spring onion and a sprig of coriander.
Serve immediately. These are delicious on their own, but also work well with chilli sauce, kecap manis or hoisin sauce.