Parsley Sauce is a simple, very old, honest English white sauce with parsley added for colour and freshness. It's very good with fish and poached foods. This sauce is all about the parsley; consequently, it is best to use fresh parsley rather than dried when you can. Still, if you had to reach for dried instead, you wouldn't be the first person. Using white pepper instead of black pepper helps avoid a fly-speck appearance in the sauce.