This calls for strong fish stock, which is basically transparent to whitish gray in color. But we want the sauce to have a reddish hue. When M. Escoffier put this recipe together, he did not have access to the very good Better Than Bouillon products, including their Lobster Bouillon. He *did* have access to a lobster stock if he wanted it. I expect to make this next week for Lorna's birthday. I will try the BtB Lobster bouillon and post a photo if it looks attractive and tastes good.