Step 1: Lightly toast your pine nuts. Place them in a dry skillet over medium-low heat. Cook, stirring constantly, for 3-5 minutes until they are fragrant and lightly golden. Immediately remove them from the pan to prevent burning and let them cool completely.
Step 2: Combine the dry ingredients. In a food processor, add the fresh basil leaves, cooled pine nuts, garlic cloves, and a pinch of salt. Pulse several times until the mixture is coarsely chopped. Scrape down the sides of the bowl as needed.
Step 3: Add the cheeses. Add both the freshly grated Parmesan and Pecorino Romano cheeses to the food processor. Pulse again a few times until the cheese is incorporated, and the mixture forms a thicker paste.
Step 4: Slowly drizzle in the olive oil. With the food processor running on low, slowly stream in the extra virgin olive oil through the feed tube. Continue processing until the pesto reaches your desired consistency – smooth but still with some texture. Avoid over-processing.
Step 5: Taste and adjust. Stop the food processor, taste your fresh basil pesto, and adjust seasoning as needed. You might want a little more salt, a crack of black pepper, or a squeeze of fresh lemon juice for brightness.
Step 6: Store your pesto. Transfer the finished pesto to an airtight container. To preserve its vibrant green color and freshness, pour a thin layer of olive oil over the surface before sealing. Store in the refrigerator for up to a week, or freeze for longer storage.