Toast the walnuts in a toaster oven for 5 minutes, or on a baking sheet in a conventional oven for 10 minutes, turning once.
Combine the basil mint and oil in a blender until smooth. Add the toasted walnuts and garlic and blend until pureed. Add the lemon juice, nutritional yeast and salt and blend once more. It's now ready to be used or stored in the fridge in an air tight container.