Mince together the fish fillets, parsnip, carrots and onions. Beat together eggs, lemon zest, sugar, paprika, salt and pepper. Add to the fish mixture and mix until well combined. Stir in 3/4 cup cold fish stock. Stir in enough matzo meal to form a moldable dough.
Once all ingredients are well combined, make into oval gefilte fish balls. Set in the refrigerator on a lined baking tray.
In large stock pot, bring the 2 litres of fish stock to a boil. Gently place the gefilte fish balls into the hot stock, cover slightly then lightly simmer for about 2 hours.
When cooked though, put fish balls into jars, then cover with the stock and chill before serving.