Over the summer months, when the garden is in full swing, I make A LOT of pesto. Much of it goes into the freezer for later use, and the rest directly into the fridge to enjoy throughout the week. We put it on eggs, pasta, homemade pizza, sandwiches, fresh summer tomatoes, mixed in plain yogurt as a veggie dip or with oil and vinegar over salad greens. There are a million ways to use it, and use it we do!
Greens: Think beyond the box. Basil is absolutely yummy. But it's only in season during the warm months. There are so many other greens that make an excellent pesto too (and I have used them all). Arugula, mustard, mizuna, kale, chives, cilantro, radish greens, turnip greens, dandelion greens, collards, spinach and my personal favorites - garlic scapes or mibuna. Hardier green like kale or collards tend to be more fibrous so use more oil with those greens. Anything goes. If it's an edible green, you can turn it into pesto.
Nuts: They aren't totally necessary, and some pesto's are just as good without them. Though the traditional pesto maker goes for pine nuts, walnuts, pecans, almonds and even pumpkin or sunflower seeds will do. As an added bonus, pumpkin seeds and sunflower seeds are MUCH cheaper and most who have nut allergies can safely eat these (always check first though!)
Olive Oil: Use a decent oil if you can- but for the sake of our food budget I never spend too much on olive oil. In a pinch I've used other oils that we have had on hand such as sunflower seed oil, but prefer the flavor of olive oil.
Cheese: Hard cheeses like parmesan, asiago and pecorino all work well, however, you can leave the cheese out entirely in a pinch (I have before) and still have a delicious pesto. I personally say, "Bring on the cheese." If you add more than less cheese, you may need to add a touch more of oil, as cheese tends to dry out your pesto.
Garlic: To each his own on how much garlic you like. Just be sure you won't be kissing anyone who hasn't had any of your pesto. If you're using garlic scapes as your green there is no need to use additional garlic at all.
Salt & Pepper: Again- to each his own! I like just a touch of saltiness, and find too much overpowers the other flavors. Course kosher salt or sea salt makes a big difference in flavor rather than table salt. We keep pepper grinders stocked and on hand, so our pepper is always fresh.
Optional Ingredients: squeeze of lemon juice, grated citrus rind, dash of nutmeg, tiny hot chili pepper... let your imagination run wild! I learned in Italy to add a dash of nutmeg and a tiny ground chili pepper to pesto, and almost always make it this way. It adds a hint of complexity and heat and is delicious. We use tiny dried chili's that we brought back from Italy and grind them with a bit of salt in a mortar and pestle. (We STILL have some left, nearly 8 years later!) Experiment!
Whatever combination of ingredients you use, drop them all into a food processor and you're practically finished. I have made pesto before without a food processor, and while it is entirely possible, it is a bit tedious. If you don't have a food processor though, it's totally worth the work.