Heat the olive oil in a large pot or dutch oven.  Add the onions, shallots, fennel, leek, garlic and ginger, saute on medium heat for about 2 to 3 minutes.  Stir in the flour with and cook until it is fully mixed in.

Add the wine, bay leaf, thyme, salt and pepper to taste.  The water and 2 tablespoons of the parsley.  Bring to a boil and simmer for about 20 minutes.  Place the frozen loaf of fish, unwrapped into the pot, bring to a boil and then lower to a simmer.  Simmer uncovered 1 1/2 to 2 hours, turning occasionally.

Transfer fish carefully to a large platter and slice.  Pull out the onions from the pot either by straining it or using a slotted spoon, discard.  Heat liquid over high heat to reduce the liquid by half, it should take about 20 minutes.  Pour over the fish and refrigerate for at least 2 hours.

Serve cold sprinkled with the rest of the parsley and a side of horseradish.

Adapted from a Joan Nathan's Fish in Parsley Sauce