Combine the basil leaves, pistachios, parmesan cheese, 3 cloves garlic, 1/8 teaspoon red pepper flakes in a blender or food processor. Blend or pulse until you have a rough chop. Gradually add in olive oil, and continue to blend until a smooth paste is formed.
Transfer to a bowl and stir in the lemon juice. Stir in salt and pepper to taste.
Serve. Great on crostini, mixed into hot noodles or couscous, instead of tomato sauce on pizza, stirred into minestrone or spread on a turkey sandwich.