Bring a large pot of water to a rolling boil on high heat.
Add potatoes, carrots, salt and seasoning sachet to the water; boil ~10 minutes, until potatoes and carrots are tender.
Add fish and continue to boil ~5 minutes, until fish flakes with a fork
Drain all in a colander; discard seasoning sachet.
Serve family style or plated; pour melted butter over all.