Combine basil, pine nuts, cheese and garlic into the blender. While the blender is running, add in olive oil a little by little. At the end add lemon juice.
Taste the pesto and adjust if needed. By adding more cheese the pesto will be creamier. And by adding more olive oil it will be thinner.
Put pesto in a jar and drizzle the top with some olive oil. You can store pesto for up to one week. Everytime you have used a bit from the pesto, drizzle the top with olive oil again. This way you can keep it for longer and fresher.