Roast the salmon with oil and salt. Cook at 350°F for 15 minutes.
Let it cool. Flake the fish into large chunks.
Heat butter and oil in a pan. Add onion, celery, and peppers.
Cook until they are very soft. Let the mix cool down.
Put flaked salmon in a big bowl. Add the cooked vegetables.
Add capers, herbs, and mustard. Toss everything together gently.
Pour in the beaten eggs. Add half of the breadcrumbs.
Mix it with your hands. Do not mash the fish.
Form the mix into small patties. Coat them in remaining breadcrumbs.
Place them on a sheet. Chill for 30 minutes.
Heat oil in a large pan. Fry cakes for 4 minutes per side.
They should be golden brown. Serve them hot.