Makes About 1 Cup
You have certainly played around with fresh basil, particularly with pesto. Here the flavor is more subtle in its cooked form.
- 2/3 cup fresh, unblemished basil leaves, packed
- 3 tablespoons best-quality extra-virgin olive oil
- 1/2-pound onions, cut in 1-inch pieces (about 1 1/2 cups chunks)
- 1 cup leek chunks (1-inch pieces)
- 2 cups water
- 1/2 teaspoon salt
Reserve 5 or 6 bright-green basil leaves (about 2 tablespoons) and 2 tablespoons of the olive oil. Put the remainder of the basil in a small saucepan with all the other ingredients (including the remaining tablespoon of olive oil). Bring the water to a boil, cover the pot, and boil gently for 15 to 20 minutes.
Remove the cover and boil steadily another 20 minutes or longer, reducing the contents of the pot to 1 cup- about a quarter of the original volume. Lower the heat if necessary, as liquid evaporates, to avoid burning the sauce ingredients.
When it is sufficiently concentrated, scrape everything from the pot into the bowl of a food processor and puree. Roughly chop the reserved basil leaves with a knife, then add the pieces to the food processor and puree until they’re incorporated. Finally, with the machine running, drizzle in the reserved 2 tablespoons of excellent olive oil, to form a light emulsion.
Serve the sauce warm with cooked vegetables; reheat on the stove if it has cooled off. Store in the refrigerator.