Mix the Matzo meal with eggs and oil, then refrigerate it for 15 minutes.
Bring a large pot of water with 1 tbsp of salt to a boil.
Using wet hands, roll the Matzo mixture into 1-inch balls (to not over-mix, or it will make the Matzo balls tough).
Carefully drop the Matzo balls in the water using a slotted spoon.
Reduce the heat to simmer and cook the Matzo balls for 30 minutes.
While the Matzo balls are cooking, add chicken stock, onion, carrots and celery to a separate pot. Bring to boil, then reduce the heat to Low and simmer for 20 minutes. Remove the onion with a slotted spoon and discard. Add salt and pepper to taste.
Carefully take out the Matzo balls with a slotted spoon and transfer them into the chicken stock. Simmer for another 10 minutes.
To serve, laddle the soup into bowls and garnish with fresh chopped dill or parsley.