Choose fresh greens, clean and well-dried
In addition to the classic choice of basil, you might consider other herbs like parsley, tarragon, mint, cilantro, and fennel fronds. You can also use many flavor-packed greens that are coming into season now, such as watercress, arugula, sorrel, and dandelions.
Make sure the herbs are clean and dry before you start. Drying them in a salad spinner, then gently blotting them with a paper towel works well. If I feel pretty confident that the herbs are free of dirt, sand, bugs and pesticide residue, I’ll skip washing them altogether.
Getting a vibrant color
Pesto is traditionally made with only raw ingredients. But since we are talking untraditional pestos, we might as well consider the "blanch and shock" method. It’s not necessary, but dropping the herbs in boiling water for a few seconds, then plunging them in ice water will bring out a vivid green color. Make sure you squeeze out all the water before proceeding.
To make a really green pesto, try adding some herbs that hold onto their bright green color. To help keep basil pesto looking fresh, for example, you can mix in some parsley.
Another way to preserve the brightness is to cover the finished pesto with a thin layer of oil before storing.
Pick garlic or other well-paired aromatics
A little raw garlic goes a long way here. While I throw in 5 or 6 cloves of garlic into a cooked sauce without hesitation, I may use just half of a garlic clove in a batch of pesto.
Keep in mind that the raw garlic flavor will grow after infusing in the pesto for a bit. Milder alternatives to raw garlic are roasted garlic, ramps, and garlic scapes.
You can also take a completely different aromatic route: try ginger, shallots, peppers, mushrooms. Or use some tapenade-style ingredients and add sun-dried tomatoes, olives, capers, or anchovies to the mix.
Give the aromatics a rough chop.
Toasted nuts add body and richness
While pine nuts are traditional, they're really expensive, plus other nuts or seeds may work better with the flavors you're using anyway. Walnuts, pistachios, sesame seeds, almonds, and cashews are some possibilities. Toasting them first always adds to the depth of the flavor (see this guide to toasting spices—it’s pretty much the same process). Be sure to cool them before adding them to the other ingredients.
Choose an oil that works with your ingredients
Extra virgin olive oil is typically used, but depending on your other ingredient, you may want a more neutral oil like grape seed, canola, or sunflower oil. Or, you might want to blend in a flavorful oil like sesame, walnut, or hazelnut oil.
Cheese is optional
The classic cheese for pesto is Parmigiano Reggiano. You can also use other hard grating cheeses, like Pecorino Romano. (Or you can use no cheese at all. Some pestos, especially those with Asian-influenced flavors, do better without cheese.)
Grate the cheese before adding it in with the other pesto ingredients.
If you're freezing pesto, hold the cheese and stir it in after defrosting for the best texture.
Pulverize the ingredients with some oil
Now that you’ve selected your ingredients, pick the equipment that works best for you: mortar and pestle, blender, immersion blender, or food processor. I like using a food processor; it’s easy, fast, and thorough.
Give larger nuts and aromatics a head start by giving them a few pulses in the food processor. Then add in the other ingredients along with a little bit of oil to help move things along. Pulse a few more times and scrape down the sides.
Drizzle in oil
Once the ingredients are finely chopped, start drizzling in the rest of the oil, with the motor running. Keep going until you have the consistency you want.
Taste and add salt or a touch of acid, if necessary. At this point, you could also swirl in some butter or crème fraiche for a richer pesto. Or, for moist and even coverage on pasta, you could thin out the pesto a little with pasta water.
Possibilities to consider
-Tarragon, pine nuts, shallots, white wine vinegar, sunflower oil with chilled asparagus and hard-boiled eggs
-Fennel fronds, garlic, parmesan, pistachios, olive oil with pasta and peas.
-Cilantro, ginger, garlic, cashews, grape seed oil, kumquats with rice vermicelli and shrimp.
-Watercress, sesame seeds, grape seed oil, mirin, and soy sauce over grilled chicken.
Oddly, a pesto that I loved but neglected to photograph was a pesto of sorrel, walnuts, fromage blanc, and walnut oil. I spread it on a burger, made a soup of it with leftover rice and chicken broth, and dipped into it with crackers. I guess I was too busy eating it to take a picture…