Preheat the broiler. Empty the mackerels. Eliminate the head. Rinse them and pat them dry.
Pepper them. Coat the inside with a little green pepper mustard. Slide in half of the fine herbs, rinsed and chopped.
Wrap them in aluminum foil. Bake for 15 minutes under the broiler, turning halfway through.
Mix the cream and the rest of the mustard. Bring to a simmer over low heat. Off the heat, stir in 1 tablespoon of chopped herbs.
Remove the mackerels from the papillotes. Sprinkle them with the remaining chopped herbs, crushed pink peppercorns, ground pepper and fleur de sel. Surround with the sauce.
Serve with a mix of white and wild rice.