Bring a small pot of salted water to a boil and prepare a bowl of ice water.

Drop the basil leaves into the boiling water for about 15 seconds, just until they turn bright green.

Use a slotted spoon to transfer them immediately to the ice water to stop the cooking.

Once cooled, drain well, then spread the basil out on a clean kitchen towel, then use another towel or paper towels to gently press the leaves to remove as as much moisture as possible.

Transfer the basil to a high powered blender with the oil and blend until very smooth, about 30 seconds or more as needed.

Line a strainer with a few layers of cheesecloth then set it over a small saucepan or bowl.

Pour the oil into the cheesecloth and let it drip through slowly without pressing. This will help to avoid excess water passing through.

Gently warm the strained oil over very low heat just until it turns a brighter green and the remaining water fully evaporates. It should become more transparent and less cloudy.

Let the oil cool completely, then transfer to a clean jar and refrigerate for up to a week.