Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
Spread the walnuts onto the prepared baking sheet and roast for 10-12 minutes, until slightly golden and fragrant. Let cool for 5 minutes.
In a food processor or blender, combine the roasted walnuts, garlic, parsley, basil, olive oil, Parmesan cheese, salt, and black pepper. Pulse until the mixture is finely chopped.
Gradually add in the water, a few tablespoons at a time, and continue to blend until the sauce becomes smooth and creamy. You can add more water for a thinner consistency.
Heat the sauce in a small saucepan over low heat for a few minutes, stirring occasionally. This will help meld the flavors together and warm up the sauce.
Serve immediately over your choice of pasta, roasted vegetables, or use as a dipping sauce.
Optional: For a richer sauce, you can add 1/4 cup of heavy cream to the mixture in the food processor before blending. Just be sure to adjust the amount of water added for desired consistency.
Notes
To make this recipe vegan, you can substitute the Parmesan cheese with nutritional yeast.For a different flavor profile, try using different herbs such as thyme or oregano.This sauce also tastes great when served chilled, making it a perfect summer dip for vegetables and chips.