Pat the salmon dry with a paper towel and lightly coat it with all-purpose flour. Season with salt and pepper.
Heat some oil in a frying pan and cook the salmon and vegetables (broccoli and cauliflower work well).
Remove the salmon and vegetables from the pan and set aside.
In the same pan, melt the butter and sauté the onion.
Add the flour and cook gently, making sure it doesn't burn.
Gradually add the milk and stir until the sauce thickens.
Add the miso and miso powder, and mix well.
Return the salmon and vegetables to the pan and coat them with the sauce.
Serve with rice and enjoy!
Adding a little red miso or Hatcho miso gives extra depth and umami. If you don't have miso powder, you can simply use more miso. Adapted from @pekocozykitchen.