Sara Moulton shares the secret to a vibrant green herb sauce

With St. Patrick’s Day looming, my first thought was that nothing would be more fitting than to salute the patron saint of the Emerald Isle with a fish dish dressed in a very green sauce, one that came by its color honestly, with no artificial food coloring allowed. A second later, it occurred to me that actually making such a dish might be easier said than done.

The problem is that bright green vegetables and herbs can quickly turn gray when cooked. They don’t like to be heated for very long and they hate acid. Meanwhile, fish — that most subtly flavored of proteins — cries out for acid.

It took bumping into several walls, but I eventually arrived at a sauce that filled the bill. This gem is packed with fresh green herbs — 4 cups (about two bunches) of parsley complemented by a quarter cup of fresh tarragon. For my first trial run, I finely chopped the herbs with a knife. The resulting sauce was mostly white with flecks of green. In pursuit of greater greenery, I confidently reached for a blender.

I threw in the whole herbs, unchopped, and pressed start. Nada. The herbs just sat on top of the blade. The third time around, I coarsely chopped the herbs before adding them to the blender. This brought them closer to the blade, but they still didn’t turn into the puree I wanted.

I’d been planning right along to add cream to the sauce at the end of the process. Now, as I climbed into the ring for the fourth round, I tried adding the cream (along with a little water) to the herbs in the blender at the beginning. Bingo! There it was, finally … a puree green as an Irish hillside.

Still, I had to be careful not to overcook it. The key is to cook the puree in a skillet with a wide bottom, which allows it to heat up in a matter of minutes. And as long as you wait until the last moment to add the fresh lemon juice, then serve the dish right away, the sauce will stay green, green, green rather than turning gray.

If you’d prefer to keep this recipe meat-free, omit the prosciutto. If you’re not a fan of tarragon, swap in basil or dill. However you customize it, this salmon will put one and all in a holiday mood.

Prosciutto-Wrapped Salmon With Fresh Herb Sauce

Start to finish: 55 minutes (40 minutes active). Servings: 4

Four 6-ounce skinless salmon fillets

2 ounces thinly sliced prosciutto

Kosher salt and ground black pepper

2 tablespoons extra-virgin olive oil

4 cups packed fresh parsley leaves and thin stems, coarsely chopped

1/4 cup packed fresh tarragon leaves, coarsely chopped

1/2 cup heavy cream

1 teaspoon cornstarch

1/4 cup minced shallots

1 teaspoon lemon juice

Heat the oven to 350 F. Line a rimmed baking sheet with kitchen parchment.

Wrap the middle section of each of the salmon fillets with a quarter of the prosciutto slices. Season the exposed part of each fillet with salt and pepper.

In a large nonstick skillet over medium-high, heat the oil. Add the salmon, reduce the heat to medium, and brown the salmon on all 4 sides, about 3 minutes total. Transfer the salmon to the prepared baking sheet, retaining the skillet. Bake on the oven’s middle shelf until slightly undercooked at the center, about 10 minutes.

Meanwhile, in a blender combine the parsley, tarragon, 1/2 teaspoon salt, cream, cornstarch and 1/4 cup water. Blend until the mixture forms a smooth puree. Set aside.

Discard all but 1 tablespoon of the oil remaining in the skillet, then heat over medium. Add the shallots and cook, stirring, until softened, about 3 minutes. Add the puree and bring to a boil, stirring. Add the lemon juice, then season with salt and pepper. Simmer for 1 minute. If the sauce becomes too thick, add a little water.

Spoon some of the sauce into the center of 4 serving plates. Set one salmon fillet onto each. Serve immediately.

Per serving: 490 calories; 290 calories from fat (59 percent of total calories); 32 g fat (10 g saturated; 0 g trans fats); 160 mg cholesterol; 770 mg sodium; 8 g carbohydrate; 2 g fiber; 2 g sugar; 44 g protein.