Have fish man grind: 5 lbs. fish filets-equal amounts; white fish and pike; and a small amount of carp or buffle carp; In a large kettle: heads, bones, and trimmings of fish; 3 onions, sliced; 1 celery stalk, sliced; 2 large carrots, sliced; water to cover; salt to taste; white pepper to taste; Bring to boil. While this is simmering prepare the fish.
Combine in Food Processor: 1 onion; 4 eggs; add mixture to: ground fish; 2 tbs. matzo meal ; salt to taste; white pepper to taste; 1/4 cup water; Shape fish mixture into balls. I used to do this by hand; chopping in a large wooden bowl with a hack messer. Be CARFUL, you don''t want mush but distinct tiny pieces.
Take another pan; and layer the beets on the bottom; some sliced carrots, onions, fish; repeat with everything but the beets. end with some carrots. Pour the broth from the OTHER kettle over the fish. Simmer, covered for 2 hours. When cool, remove fish balls to platter and garnish with sliced cooked carrots. Strain broth and chill.
Serve with jellied fish broth and fresh ground horseradish.
NOTE: The beets are unusual but my Mom and Bubbe ALWAYS used them. They do two things; keep the fish from ''catching'' on the bottom and give the broth a ruby red color; but not the fish; they remain white.
I have never served it with anything but plain freshly grated horseradish.