In a food processor, or high powered blender, place walnuts, garlic cloves, rocket, parmesan cheese and chilli flakes. Pulse until all ingredients are finely chopped, regularly scraping down the sides
Drizzle in olive oil as you pulse the other ingredients. Pesto should still be textured, but silky enough to be used as a sauce or dip. Season with salt as needed. The taste of the pesto varies based on the ingredients, so taste regularly throughout.
Store in the refrigerator in an airtight container or jar for up to one week. Perfect with fresh pasta, on a sandwich with chicken and brie, or as a part of a cheese board.