What Makes a Great Pesto, According to an Expert

Pesto, that beguiling, fragrant, emerald green sauce of pounded basil leaves, garlic, pine nuts, olive oil, and Parmigiano cheese, is one of Italy's most famous contributions to the culinary world. And it is the defining flavor of Liguria, the rugged coastal sweep of northwestern Italy where it originated. Tossed with freshly cooked pasta, drizzled on poached or baked fish, dolloped on vegetable minestrone, pesto has the power to brighten and enliven any dish it meets. If you've only ever tried jarred pesto, do yourself a favor and make a homemade batch. It's easy to do if you follow a few key steps. Once you've tried it, you'll wonder how you ever lived without it.

What Is Pesto?

The word "pesto" comes from the Italian verb "pestare," which means "to pound." Simply put, pesto is a raw sauce or mixture made by pounding various ingredients together in a mortar and pestle. The vibrant green basil sauce that the word "pesto" conjures for most of us is pesto alla Genovese. It gets its name from the city of Genoa, the hilly capital of Liguria where basil is cultivated in profusion, and where the sauce is believed to have originated sometime in the 17th century. The other ingredients in traditional pesto are garlic, pine nuts, salt, olive oil and Parmigiano cheese, or a mix of Parmigiano and pecorino cheeses.

There are many iterations of pesto, both traditional and nontraditional. Pesto alla Trapanese, named for the city of Trapani, in Sicily, swaps in almonds for pine nuts and adds a handful of cherry tomatoes. There's also arugula pesto, cilantro pesto, parsley pesto, lovage pesto, sun-dried tomato pesto, spinach pesto, tarragon pesto, roasted tomato pesto and more.

To make traditional pesto, look for young basil, with leaves no bigger than the pad of your thumb. Mature basil has a strong flavor and is too "woody" to be pounded to a creamy consistency. To make it, pound the ingredients, first separately and then together, using a marble mortar and wooden pestle, until everything is reduced to a creamy sauce.

Nowadays, a food processor or bullet blender usually takes the place of the mortar and pestle and makes quick work of the task, grinding and pureeing everything together.

What Is Pesto Made Of?

Pesto contains just a few ingredients: fresh basil leaves, garlic, pine nuts, salt, olive oil and Parmigiano-Reggiano cheese.

True pesto Genovese is made with Genovese basil from the hills of Genoa, harvested while the leaves are still small and very tender; mild garlic (ideally from nearby Vessalico); pine nuts (all the better if they come from the area around Pisa); coarse sea salt; buttery, mild olive oil from Liguria; and Parmigiano-Reggiano cheese, or a mix of Parmigiano and Pecorino Sardo, an aged sheep's-milk cheese from Sardinia.

Those of us who love pesto but live nowhere near Liguria can be less picky about the provenance of the ingredients we use.

What Does Pesto Taste Like?

If the Garden of Eden had a flavor, it would be pesto: sweet, floral, salty, rich, herbaceous with a slight tinge of bitter. Properly made pesto tastes fresh and zingy and balanced, not muddy. Each flavor component is identifiable—the fragrant basil, the pungent garlic, the buttery olive oil and sweet pine nuts, the tangy cheeses—and yet none dominates. Basil is the star, for sure, but its perfume works in balance with the other ingredients.

What's So Special About Pesto?

There's a magical quality to pesto. Tossed with hot pasta, its flavor becomes more vibrant as it warms from the residual heat. Dolloped into a bowl of minestrone, it brightens the taste of the vegetables. It can jazz up simple baked fish, and it's heaven on a tomato-and-mozzarella sandwich. It's a versatile sauce that pairs well with many flavors and dishes.

Pesto is also ideal for creative culinary riffing. While basil is the traditional herb for pesto, nothing says you can't improvise. Why not add a handful of mint from that giant mound in your garden? Or use the bunch of parsley that's been sitting in your crisper drawer? No pine nuts? Try buttery, slightly bitter walnuts instead. I like to make "white" pesto with walnuts, a small amount of fragrant herbs—basil and marjoram—and a few dollops of fresh ricotta cheese.

How Do You Eat Pesto?

The most common way to enjoy pesto is with pasta. In Liguria, traditional pasta shapes for pesto include trofie, a small corkscrew shape; trenette, similar to linguine; gnocchi; and corzetti, an embossed coin shape. Pesto for pasta is not meant to be cooked, but rather tossed raw with just-cooked pasta, along with a splash of cooking water.

Of course, there are countless other ways to put your pesto to use. Spread a little on top of grilled eggplant, mushrooms or peppers. Use it to season chicken salad or potato salad, or as a filling for stuffed chicken breasts. Thin it with a little oil and drizzle over a fresh caprese salad. It's also a delicious flavor bomb for homemade pizza, focaccia and bread.

Is Pesto Healthy?

According to Emily Lachtrupp, M.S., RD, "Pesto contains leafy greens from the basil and healthy fats from olive oil and pine nuts, making it a nutritious choice. Plus, it's packed with flavor, so a small serving goes a long way." Store-bought pestos tend to be high in sodium, so be sure to check the nutrition label when browsing your options. You can control the sodium by making your own.

Though nutrition will vary from brand to brand, here's the nutritional breakdown for 1 tablespoon of typical store-bought pesto, according to the USDA:

• 93 calories
• 0g fiber
• 0g sugar
• 1g protein
• 9g total fat
• 2g saturated fat
• 3mg cholesterol
• 158 mg sodium
• 32mg potassium

How Long Does Pesto Last in the Refrigerator?

Although pesto can be stored in the refrigerator, its vibrant green color turns dark and murky quickly when exposed to air. To prevent discoloration, scoop the pesto into a small container and cover it with a thin layer of extra-virgin olive oil. Store in the fridge for up to three days.

Can You Freeze Pesto?

For longer storage, you can freeze pesto; it will last in the freezer for up to six months. Although you can store it in a single container, it's more convenient to portion it out between smaller airtight containers or sealable bags, which allows you to retrieve only as much as you need. You can also freeze pesto in an ice cube tray. Once frozen, pop out the individual portions and transfer them to a sealable freezer bag or airtight container and return to the freezer. This gives you conveniently small portions perfect for flavoring soups, dressings, sauces and more.