Mix the herbs with the spices and coat the fillets on both sides. Cover and leave in the refrigerator for 24 hours. Later, remove the herbs and cut the fillets into thin strips. For the sauce, whisk all the ingredients except the mustard in a bain-marie until creamy, then carefully fold in the mustard. Divide the fillets evenly on plates and add the mustard sauce. Serve with cooked, peeled potatoes.
Our tip: As an alternative to fresh herbs, you can also use frozen ones – these are also characterized by a fresh taste!