In a large pot of water, over high heat, add 1 teaspoon salt and bring to a boil. Prepare an ice bath of ice and water. Add the basil leaves into the boiling water, cook for 10 seconds and remove immediately to ice bath. When cool, transfer to a salad spinner or strainer and remove water.
Add leaves, remaining teaspoon of salt and oil into a blender and pulse to puree. Scrape down the sides and pulse a few more times. Strain mixture through 4 layers of rinsed cheesecloth into a sterile canning jar (16 ounce size is good). This process will take about an hour.
Refrigerate unused portion for up to a week.