Parsley sauce can mean different things to different people, but for me it is this British-style parsley sauce with cream and a hint of mustard. It’s great on fish, white meat poultry, or pork.

Lots of other versions of parsley sauce exist around the world. One of the most famous is chimichurri, from Argentina, and parsley plays a huge role in Italian salsa verde. These are both acidic sauces with no dairy.

This version, which is common all over the United Kingdom, bears a closer resemblance to French sorrel sauce, which is pretty close. Both are cream/milk based, and both get their zing from something other than citrus or vinegar, although you can use a little lemon in this recipe.

The flavor of this sauce is, naturally, strongly of parsley, tamed by the dairy, with undertones of mustard/horseradish, plus a very slight brightness from a touch of lemon, or the vinegar in the prepared horseradish.

If you are familiar with French mother sauces, this one starts as a béchamel, a flour-and-butter roux mixed with whole milk and/or cream. You add some zing to it — black pepper or white, powdered mustard and/or prepared horseradish — then lots of minced fresh parsley.

That’s about it. Super easy. A few pointers:

• Use whole milk plus some heavy cream, or half-and-half. If you try to make parsley sauce with skim milk, it will likely break and look (and taste) awful. These fattier dairy products can also withstand the hit of lemon juice or vinegar without curdling.
• Either curly or flat-leaved parsley work. I grow flat-leaved parsley and often have enormous amounts of it, thus this sauce.
• I really like to use powdered Chinese mustard because it’s stronger, but regular Coleman’s or some other supermarket brand is fine. Start with my recipe below and add it by the 1/2 teaspoon if you want a stronger flavor.

Given how easy this all is, you can sub in other herbs and get different effects. Some excellent options would be lovage, tarragon, cutting celery, cilantro, mint, fresh oregano, watercress or summer savory.

I use my parsley sauce mostly on fish (as you see in the pictures) or white meat poultry like pheasant, quail, grouse or wild turkey; obviously chicken is fine. Rabbit is another great choice, and pork loin works well, too.

Once made, you really want to use your parsley sauce right away. Like other gravies, it will set up and congeal after a while. You can store it in the fridge for a day or two, though. Reheat it slowly on the stove and add a little extra milk or cream to thin it to the correct consistency.