Blender Pesto
Source: The Classic Italian Cook Book by Marcella Hazen Makes enough for about 6 Servings of pasta

2 cups fresh basil leaves (see note below)
1/2 cup olive oil
2 tablespoons pine nuts
2 cloves garlic, lightly crushed with a heavy knife handle and peeled
1 teaspoon salt
1/2 cup freshly grated Parmesan cheese
2 tablespoons freshly grated Romano pecorino cheese
3 tablespoons butter, softened to room temperature

Put the basil, olive oil, pine nuts, garlic cloves, and salt in the blender and mix at high speed. Stop from time to time and scrape the ingredients down toward the bottom of the blender cup with a rubber spatula.

When the ingredients are evenly blended, pour into a bowl and beat in the two grated cheeses by hand.

When the cheese has been evenly incorporated into the other ingredients, beat in the softened butter.

Before spooning the pesto over the pasta, add to it a tablespoon or so of the hot water in which the pasta has boiled.

Note: The quantity of basil in most recipes is given in terms of whole leaves. American basil, however, varies greatly in leaf sizes. There are small, medium, and very large leaves, and they all pack differently in the measuring cup. For the sake of accurate measurement, I suggest that you tear all but the smallest leaves into two or more small pieces. Be gentle, so as not to crush the basil. This would discolor it and waste the first, fresh droplets of juice.