Melt the butter in a heavy-bottom saucepan. Add the carrot and onion, and cook over low heat for 5 minutes, while stirring occasionally. Add the thyme, bay leaf, parsley stems, fish bones and peppercorns.
Cover and steam for 10 minutes over medium heat. Pour off the excess butter. Add the wine and fish stock.
Reduce over medium heat for 10 minutes. Season with Knorr seafood stock mix. Bring the sauce to a boil and simmer for 5 minutes.
Strain the sauce through a fine strainer, pressing the bones to extract all the sauce.
Serve this sauce with baked and poached salmon.