Place the softened butter in a small bowl and mash it with the ras el hanout.
Dice the preserved lemons as finely as you can and place them in a bowl.
Peel the garlic cloves and mash them into a paste, and add them to the preserved lemon.
Chop the parsley as finely as you can and add it to the preserved lemons and garlic mix.
Add the olive oil for the sauce to the bowl along with the sumac, give it all a mix and have a taste, add salt if required, but it should not be needed.
Season the mullet with the salt.
Heat a 30cm or 12" frying pan over a high heat and add the oil when it is hot.
Pan fry the mullet, skin side down, for 2-3 minutes, flip the fish and add the butter and ras el hanout mix and cook for another minute, basting the fish for another 90 seconds.