Recipe for Poached Fish with Mustard Sauce – Oma's Fisch mit Sosse

This recipe for poached fish, aka pochierter Fisch, has a mustard sauce. Poaching keeps the fish moist and provides for the base for the sauce. Instead of using flour or cornstarch to thicken the sauce, the poaching liquid is reduced. The resulting sauce is thickened by stirring in some butter at the end.

Prep Time

10 minutes

Cook Time

35 minutes

Total Time

45 minutes


Makes 4 - 6 servings


  • 1½ pounds cod fillets
  • 2 tablespoons lemon juice
  • 1 small onion, sliced
  • ¼ cup chopped parsley, keep stalks separate
  • 6 whole peppercorns
  • 1 clove
  • 1 bay leaf
  • 5 cups water
  • 2 tablespoons Dijon mustard
  • 6 tablespoons butter
  • salt, pepper


  1. Sprinkle lemon juice on fillets.
  2. Put the onion, peppercorns, clove, parsley stalks, and bay leaf in a large frying pan.
  3. Pour in water and bring to boil. Cover and simmer for 20 minutes.
  4. Add fish, cover, and simmer very gently for about 10 minutes or until fish flakes.
  5. Remove fish (cover with foil to keep warm)
  6. Strain 2 cups of poaching liquid into a pan and simmer until reduced to about half. Stir in mustard.
  7. Whisk butter into reduced stock, a little at a time - this will thicken sauce slightly. Season with salt and pepper.
  8. Return fish briefly to poaching liquid to re-warm. 
  9. Serve fish with sauce.

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