In a food processor, blend softened butter until it has a creamy texture.
Add grated Parmesan cheese, peeled garlic cloves, fresh basil leaves, nuts (pine nuts or walnuts), and salt and pepper to taste.
Blend on medium speed for about two minutes or until the mixture is smooth and spreadable.
Use a spatula to scrape down the sides of the bowl and ensure all ingredients are evenly combined.
Transfer pesto butter to an airtight container and refrigerate for up to five days. Flavors will continue to develop over time. Enjoy on toast, pasta, or as a savory spread!