In the bowl of a food processor or blender, add all the ingredients from the basil leaves through to the red chili flakes (everything except the olive oil).
Blend to combine until basil is chopped up. Then, drizzle in the olive oil while blending until all the olive oil is added and a paste with some texture forms. Taste and adjust seasoning as desired.
Store in a tightly covered jar covered with a thin layer of olive oil in the fridge for up to 2 weeks, or freeze for up to 6 months (instructions in the post)