Crack the egg into a medium bowl and whisk with a fork
Use your hands to break up the leftover salmon into flakes and add to the bowl
Stir together gently with a fork until you can make a small ball in the palm of your hand. Don't over stir it still want to see some flakes! Set mixture aside.
Shape the salmon mixture into about five, even palm-size balls and set aside.
Add a third a cup of Panko bread crumbs to a plate and season with salt and pepper. (Add some dried parsley or garlic powder if you want!)
One at a time, flatten a ball gently into the Panko breadcrumbs. Gently flip it over and press it into the panko on the other side, to coat both sides.
Since this is a loose, flaky mixture, it will try to fall apart on you. Turn it on its side and roll it into a hockey puck shape to coat all around the edges. You will probably need both hands to do this. Once it looks like a panko-coated hockey puck, lightly spray it with cooking oil and set it on the greased baking rack.
Gently spray the other side with cooking oil. This will help brown and crisp the salmon cakes.
Place the salmon cakes and rack on top of the cookie sheet and bake about seven minutes, or until slightly browned on top.
Flip cakes gently and place back into the oven for another seven minutes. Remove salmon cakes from oven when they are lightly browned on both sides. When you press lightly with a finger, they should not be squishy.
All we need to do here is cook the egg through since the salmon has already been cooked! Once they are cooked through, remove from the oven.
They can be served plain, or squeeze fresh lemon over the top! You can also put them in a burger bun and make a salmon burger!