Place the pistachios in a food processor and pulse until they are broken down into small pieces.

Add the garlic and basil and turn the food processor on.

While the food processor is running, slowly add the olive oil until the pesto is thickened to your liking.

Add the lemon juice, salt, and pepper and pulse once more to combine. Store in an airtight container in the fridge. Use within 1 week. Note: For a thick pesto, use only ½ cup (120 ml) extra virgin olive oil. For a thin pesto, use 1 cup (240 ml) extra virgin olive oil.