Why It Works
- The potato adds extra starch to the pasta water, helping to bind the sauce and absorb excess oil from the pesto.
- Tossing it all together off the heat preserves pesto's fresh flavor.
As any screenwriter, author, or comic writer will tell you, there's no better way to get your audience coming back for more than to end with a gripping cliffhanger. In this moment alone, I'm tortured as I wait to find out what will happen now that Rey has found Luke, how Jon Snow will come back from certain death, whether Rick really has a good plan for dealing with the Whisperers, and what the heck Kenji has in store for us in the follow-up to his first book. I'm clearly a sucker for serialized narratives.
If I were smarter, I would have capitalized on this fact when I wrote my original article on how to make the best pesto sauce, because it was only half the story. I didn't point it out at the time, but astute readers may have noticed that I left out a huge chunk of information. Specifically, how to serve the pesto on pasta.
That may not sound like a major omission at first. It's not like it's difficult to put pesto on pasta and eat it. And yet, pesto is actually an interesting pasta outlier, because it's a sauce that breaks SPOP (Standard Pasta Operating Procedure). What is SPOP? Well, it usually goes something like this:
- Step 1: Start by warming the sauce—whether a premade sauce, like ragù, or a quick-cooking pan sauce, like clam sauce—in a skillet.
- Step 2: Transfer the cooked pasta to the skillet with the sauce, adding some pasta-cooking water, little by little, while boiling it all together over the heat and stirring vigorously.
- Step 3: When the sauce has thickened to nearly a noodle-coating consistency, remove it from the heat and work in cheese, extra oil, and/or butter while stirring and tossing rapidly.
- Step 4: Eat.
There are some possible variations on SPOP, but the overall idea holds: Finish the pasta in the sauce over the heat. It's possibly the single most important thing to learn if you want to improve how your pasta turns out.
Only, with pesto, SPOP is OOTQ.
The Most Important Rule of Cooking With Pesto: Don't Cook It
In a departure from almost every other pasta sauce out there, all the charm of pesto is dependent on its fresh, raw flavor. Heat, and in particular prolonged exposure to high heat, is just about the worst thing for it. That's why most store-bought pesto is so disappointing: The high-heat sterilization necessary for canning and bottling cooks the basil, turning its volatile anise-mint scent dull.
So, instead of SPOP, you should follow SPOP (Standard Pesto Operating Procedure).*
*You can blame the red tape and bureaucrats at PASTY (Pasta Associative Society of Timbuktu and Ytaly) for coming up with the same acronym for two opposing procedures.
Here are the steps:
- Step 1: Boil pasta until al dente.
- Step 2: Transfer pasta to a mixing or serving bowl.
- Step 3: Add pesto.
- Step 4: Add pasta water bit by bit, mixing to bind and emulsify the oil-based sauce.
- Step 5: Eat.
Clearly, there's still heat in this process—the pasta is hot, and the pasta water is just off the boil—but it doesn't have the same impact on the basil's freshness as it would if you were to continuously cook it all together over the heat, following the primary SPOP procedure.
But Wait, There's More! (The Mystery of Potatoes and Green Beans)
Now, if I were clever, I'd stop here, leaving you wondering what in the world this mystery could be. That would be a successful cliffhanger. But I'm not going to toy with you like that, even if it puts a dent in my ratings. I'll get right to it: Travel to Genoa, capital of true Ligurian pesto, and you're likely to see it served with pasta, potatoes, and green beans, all cooked together in the pot.
What in the world is up with that?
It's hard to get a clear answer. Most of my cookbooks fail to shed any real light on it, so I turned to Italian food blogs and their (sometimes passionate) comments sections to see if I could come up with a better explanation.
Some sources claim that, when served with potatoes and green beans, pesto pasta is known as avvantaggiato, which I might very loosely translate as "tricked out"—the idea being that those additional ingredients are a bonus.
Others say this is all wrong, and that "avvantaggiato" should actually be avvantaggiate, in that the adjective should refer not to the pesto, but to a specific type of pasta that's often served with pesto: trenette, a linguine-like noodle. Trenette, when dubbed "avvantaggiate," are made with whole wheat, the benefit presumably being the addition of the wheat's bran.
And then, of course, there are those reasonable beings who are willing to accept that both meanings can coexist.
Either way, potatoes and green beans are a popular addition, no matter what it's called. Beyond that, there's plenty of argument about what type of pasta to serve with pesto when adding potatoes and beans. One commenter in this thread insists that, despite all the pasta types classically associated with pesto, potatoes and beans are only appropriate with the dried ones, like trenette or mafalde, but not fresh ones, like trofie (Ligurian gnocchi made with potato and flour), trofiette (a small twisted wheat pasta), and mandilli de saea (tissue-thin, lasagna-like sheets). But, as you might expect, plenty of other sources contradict that; I've found examples of the potato-and-bean combo with just about every pasta shape.
There's enough disagreement around all of this that I'm willing to just give it a pass—argue away, Italians, I'll be eating a nice bowl of pasta with pesto while you do. Still, the question of why to add potatoes and beans lingers. I've long assumed that the potatoes are there for their starch: In a dish that isn't finished (and emulsified) over the heat, any extra starch would be welcome, helping to absorb some of the pesto's oiliness and bind the sauce. I'd never confirmed my theory until recently, when I found the same explanation on several websites, including that of the Genovese Pesto Consortium. This article, meanwhile, analyzed several brands of mass-market pesto sauce available in Italy and found that many of them include potato in their ingredients, the purpose specifically being to simulate the creamy texture of the dish when made with potatoes.
I've been adding potatoes to my pesto pasta for years, almost always choosing russets for their high starch content. While recipe-testing for this article, though, I decided to give Yukon Golds a try and decided I like them more. They add just enough starch, but aren't as powdery and crumbly as russets, delivering a more balanced, less pasty result.
As for the green beans, I'm still at a loss, aside from the simple reason that they taste good and add a tender element to an otherwise starchy dish. Maybe that's all there is to it?
Tell you what: I promise to dig even deeper and reveal my findings...next time.
[To Be Continued...]
- Kosher salt
- 1 pound (450g) dried pasta, such as trenette, linguine, or mafalde
- 5 ounces peeled Yukon Gold potato (140g; about 1/2 medium), cut into 3/4-inch cubes
- 4 ounces (110g) green beans or haricots verts (about 20 green beans or 30 haricots verts), stems trimmed and cut into 1-inch lengths on a bias
- 1 recipe pesto sauce
- Extra-virgin olive oil, for drizzling
- Grated Parmigiano Reggiano, for serving
In a large pot of salted boiling water, boil pasta, potato, and green beans until pasta is al dente and potato and green beans are very tender. Drain, reserving 1 cup cooking water, and transfer pasta, potato, and green beans to a large mixing or serving bowl.
Add pesto sauce to pasta along with 1/4 cup pasta cooking water. Toss well to emulsify pesto and pasta water into a creamy sauce. Add more pasta water, 1 tablespoon at a time, as needed, if pasta is too dry. Drizzle in fresh olive oil, if desired. Serve with Parmigiano Reggiano on the side.