Add the basil leaves, garlic, pine nuts, and salt to the bowl of your food processor fitted with the blade attachment. Pulse 4-5 times until coarsely chopped. Then with your food processor running, slowly drizzle in the olive oil and process until well combined. Transfer the pesto to a clean container. Cover and refrigerate it until you're ready to use it. The pesto can be made 1-3 days in advance.