Skim off any foam that rises to the surface. Reduce the heat to maintain a simmer, cover and simmer for at least 45 minutes before poaching the quenelles. Place the fish parts, salt, onions, carrots, sugar and water in a large stockpot and bring to a boil.Gefilte terrine mixture from Baked Terrine recipe (see steps 1 and 2).Heads, bones and tails from a fish (see Note).The poaching liquid can be made without these fish parts, but the gefilte quenelles will be slightly less flavorful. Note: If poaching, a fishmonger can save the head, bones and tail for you if they sell you the fillet-just ask. Cool to room temperature before removing from the pan and slicing. The terrine is finished when the corners and ends begin to brown. Place the loaf pan on a baking sheet on the middle rack of the oven and bake for 40 to 45 minutes.Line an 8×3-inch loaf pan with parchment paper and fill the pan with the fish mixture. Scoop into a bowl and give it an additional stir to ensure that all the ingredients are evenly distributed throughout. Pulse in the food processor until the mixture is light-colored and evenly textured throughout. Add the fish fillets to the food processor along with the rest of the ingredients, except for the horseradish. Place the onion in the bowl of a large food processor and process until finely ground and mostly liquefied.You can buy your fish preground from a fishmonger (usually a Jewish fishmonger) to ensure all the bones are removed, but try to cook your fish that day since ground fish loses its freshness faster. If there are any bones left in your fillets, remove the larger ones by hand, but don’t fret about the smaller ones since they’ll be pulverized in the food processor.Horseradish relish, store-bought or homemade, for serving.2 tablespoons coarsely chopped fresh dill.2 tablespoons coarsely chopped fresh watercress (or spinach).1¼ tablespoons vegetable or grapeseed oil.12 ounces whitefish fillet, skin removed, flesh coarsely chopped.Makes one small terrine, serving eight to 10 Ingredients

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