First toast your walnuts! Heat your oven or toaster oven to 350°F and spread walnuts, spaced on a baking sheet. Roast for 5 to 10 minutes, shaking/tossing the pan occasionally to ensure even cooking.
Add walnuts and garlic to your food processor. Pulse until both are minced.
Next add kale, spinach (or basil), salt, juice of one lemon, and optional parmesan cheese. Blend well, adding the olive oil through the top of the processor towards the very end and gently blending to incorporate.
Since everyone's perfect pesto varies, feel free to adjust seasoning to taste as well as the liquid to veggie ratio, an extra drizzle or two of olive oil can thin the sauce as desired. I usually snag a piece of crusty bread and dunk as I taste test, it's glorious!
Notes
Try to choose an olive oil you love the taste of, a quality oil is key here!See post for some tasty serving suggestions for kale pesto.