The basic ingredients in pesto sauce are basil, olive oil, pine nuts, garlic cloves, Pecorino Romano and Parmesan cheese. To make a pesto sauce, either combine the ingredients in a food processor, or go the traditional route and use a mortar and pestle.
While many recipes for pesto sauce in the United States call for just grated Parmesan cheese, traditional pesto sauce, originating from Genoa, Italy, calls for both Parmesan and Pecorino cheeses. If they are available, use Parmesan-Reggiano and Pecorino Fiore Sardo cheeses specifically for the most authentic pesto sauce.
To make pesto sauce with a food processor, add 2 cups of basil leaves, 2 cloves garlic and 1/4 cup pine nuts to a food processor. Pour 2/3 cup olive oil into a container, then add half of it to the food processor. Process the ingredients to a coarsely chopped mixture. Slow pour in the remaining olive oil and pulse until smooth. Transfer the pesto sauce to a serving bowl and stir in 1/2 cup of grated Pecorino and/or Romano cheese before serving. Season with optional salt and pepper to taste.
To make pesto sauce by hand, add 3 tablespoons pine nuts, 2 cup basil leaves, 1 clove of garlic and a pinch of salt to a large stone mortar. Grind the ingredients together with the pestle, until you get a paste. Add in 1/4 cup grated Parmesan and 3 tablespoons Pecorino cheese. Slowly drizzle in about 10 tablespoons of olive oil before serving.