Preheat the oven to 325℉, and grease a 12-cup bundt pan with cooking spray.

Dice the onions, and shred the carrots on a box grater. Sauté them in the oil over medium-high heat until the onions are golden and soft. Set them aside to cool.

If you can have someone at the fish market grind the fish, all the better. Otherwise, you can pulse it in a food processor fitted with a steel blade, making sure you remove the membranes that may attach themselves to the blade—or use the grinding attachment of a stand mixer.

Put the cooled onions and carrots into the bowl of a stand mixer fitted with the paddle, along with the ground fish and the eggs, matzo meal, salt, white pepper, sugar, ½ cup (118 ml) water, and herbs. Mix at medium-low speed for about 10 minutes, or until everything is well blended and smooth.

Pour the mixture into the prepared bundt pan, and smooth out the top. Set the filled Bundt within a larger pan with 2 inches of warm water up the sides of the Bundt. Bake for about an hour, or until the center is solid and a toothpick inserted near the middle comes out clean.

Cool for about 15 minutes, blot away any water on top, and run a knife around the edges of the pan. Swiftly invert the gefilte fish onto a flat serving plate.

Refrigerate it for several hours or overnight. Slice it as you would a torte, garnish the slices with parsley, and serve with horseradish sauce, either red or white. Leftovers keep for about 5 days.