In a dry skillet over medium heat, toast ½ cup of walnuts until golden and fragrant. Then remove from heat.
In a food processor, pulse the toasted nuts until they’re completely broken down. Add 2 cloves of garlic cloves and ¾ cup of extra-virgin olive oil; pulse until garlic is finely chopped.
Thoroughly wash 2 cups of arugula under cool, running, drinkable water.
Add the herbs, ½ cup grated Parmigiano-Reggiano, and juice from ½ lemon and process until smooth in your food processor. Stop and scrape down the sides with a rubber spatula and process again until well blended.
Taste and add kosher salt if needed—the Parmigiano-Reggiano is naturally quite salty, so you often won’t need to add much extra salt!
To store in the fridge, put pesto in a container and top with a layer of extra-virgin olive oil. To store in the freezer, scoop the pesto into an ice cube tray and freeze into cubes. Your future self will thank you kindly.