Melt 1 Tbsp of butter in a medium sauce pan    Stir in 2 Tbsp of flour – constantly stirring and not letting the flour and butter brown   Let it cool and add add 1 cup of hot fish bullion    Mix well to get rid of lumps and add the rest of the bullion, mixing well each time    Bring the sauce to a boil and add 1 thinly sliced onion along with one parsley sprig    Simmer for 30 minutes    Season with 1/2 tsp lemon juice and add salt to taste    Strain the sauce and serve over your favorite (maybe poached) fish