Ask your fishmonger to fillet the fish, reserving the bones and heads.

Request an extra fish head for a richer broth.

Coarsely grind the fish with 2 onions in a grinder or processor.

Transfer the mixture to a bowl and continue chopping.

Incorporate 2 tablespoons of salt, 1 tablespoon of sugar, matzo meal, and eggs.

Add water gradually to create a smooth, light paste.

In a large pot, place fish heads and bones, carrots, pepper, remaining salt, sugar, and one onion.

Cover with water and bring to a boil.

In a separate pot, boil 3 quarts of water.

When the fish bone broth boils, prepare fish balls.

Moisten hands with cold water and form spheres.

Drop the fish balls into the simmering fish bone broth.

Simmer for 1.5 hours, adding water as needed.

Remove from heat and let the fish balls cool in the liquid.

Remove fish balls with a slotted spoon to a serving platter.

Strain the cooking liquid.

Pour it into a jar and refrigerate until cold and gelled.

If it doesn't gel, rewarm the liquid and dissolve gelatin.

Test the gelatin setting with a teaspoon on a plate.

Add more gelatin if necessary until it gels.

Refrigerate until chilled.

Serve the fish cold with the fish aspic and chrain (horseradish).