From Mustards: Napa Valley Cookbook (Canada, UK), by Cindy Pawlcyn.
Here is a very simple way to use a whole bunch of basil, and the result has multiple uses. It is good on pasta or mashed potatoes, or to dress up a soup. Fold a little into some mayonnaise or aioli to use as a sandwich spread or to top grilled fish. Or, try working a bit of pesto into a vinaigrette for a different flavor.
2 cups loosely packed fresh basil leaves (about 1 bunch)
4 or 5 cloves garlic
1/3 cup grated Parmesan or aged dry Jack cheese
1/4 teaspoon salt
1/8 teaspoon freshly ground black pepper
1/2 cup olive oil plus 1 to 2 tablespoons (optional)
Combine the basil, garlic, cheese, salt, and pepper in a blender or food processor and process briefly. With the motor running, add 1/2 cup oil in a slow, thin stream. Continue processing until the pesto is the texture you prefer. If you plan on keeping this for a while in the refrigerator, float a tablespoon or so of oil across the surface to keep the top from turning dark, then cap tightly. It should keep until it's all used up. Serve at room temperature.
Yield: Makes about 3/4 cup