Sorrel sauce is a classic French cream sauce that uses the tart, lemony potherb commonly known as sorrel (Rumex acetosa) as the defining ingredient. Oxalic acid, a naturally occurring compound in the plant, gives it this flavor. In small quantities sorrel makes a bright, lip-puckering addition to salads, soups, or sauces—but too much oxalic acid can be mildly toxic and hard on the digestive tract.
Turns out you don't have to grow sorrel to get this singular flavor. Another unrelated species of plant grows wild in the woods and also contains oxalic acid. Funnily enough it's called oxalis—or sometimes wood-sorrel.
Maybe you've seen wood-sorrel before. It looks like the sort of shamrock that would bowl over a leprechaun. Large patches of it will sometimes carpet the forest floor. Here in the Pacific Northwest the species I usually see is Oxalis oregona. Something about the lobed leaves and dense matting is comforting to me. When I see a big patch of oxalis I just want to dive in and float on my back.
While most fish pair well with a sorrel sauce, salmon is perhaps the most celebrated. I picked up a fillet of wild spring chinook at a rather hefty price so I could properly enjoy this sauce that cost pennies to make.
2 half-pound wild salmon fillets, skinless
2 tbsp cold unsalted butter, divided
1 small shallot, diced
1/4 cup champagne vinegar
1/8 cup heavy cream
small pinch cayenne pepper
1/4 cup packed wood-sorrel leaves, de-stemmed
salt and pepper
1. Brush the salmon fillets with olive oil, season with salt and pepper, and place on foil on a baking sheet. Put fillets in pre-heated oven on broil, 4 to 6 inches from flame, just before making sauce. Figure about 10 minutes per inch of thickness.
2. Over moderate heat melt 1 tablespoon of butter in a heavy, nonreactive saucepan. Add diced shallot and cook, stirring, until starting to brown, 1 or 2 minutes.
3. Add champagne vinegar and reduce to a tablespoon before adding heavy cream. Bring barely to boil, reduce heat, and stir in second tablespoon of butter. The sauce should be thick. Season with salt and a pinch of cayenne pepper.
4. Quickly shred wood-sorrel leaves and mix into sauce. The leaves will lose their vibrant green color but their distinct lemony flavor will remain. Pour over salmon fillets and serve immediately.
Makes 2 servings.
You can also enjoy wood-sorrel as a garnish. It's especially nice as a contrast to the rich, buttery flavor of a good cut of beef.