Toast the walnuts in a skillet over medium heat for 3–5 minutes until golden brown and fragrant. Let cool.

In a food processor, combine cooled walnuts, fresh sage, Parmesan cheese (or nutritional yeast), and garlic. Pulse until coarsely combined.

With the processor running, slowly drizzle in the olive oil until smooth and creamy. Adjust consistency with a splash of water or more oil as needed.

Taste the pesto and adjust seasoning with salt and pepper as necessary.

Transfer to an airtight container. Store in the fridge for up to a week or freeze in ice cube trays for longer preservation.