fresh basil leaves, photo by: gourmetsleuth.com

I N G R E D I E N T S
3 cloves garlic, cut into pieces
2 cups solidly packed fresh basil leaves (or 1 cup solidly packed basil leaves and 1 cup solidly packed parsley)
3/4 teaspoon coarse salt
freshly ground pepper
1/2 cup extra-virgin olive oil
1/3 cup pine nuts
3/4 cup Parmigiano Regiano
2 tablespoons softened (room temperature) unsalted butter

1 tablespoon softened butter (for serving with the pasta)

I N S T R U C T I O N S
You can use a food processor or a large, sturdy mortar and pestle.  This is also a very good job for a Thai Stone mortar and pestle.

Food Processor
If using a blender, place all the ingredients except the cheese and the butter. Blend to a smooth puree (don't overblend).  Transfer to a bowl, and the parmigiano and beat the cheese in using a wooden spoon. Add the butter and beat the mixture until it is smooth.   Cover and set aside.  At this point you can refrigerate the pesto and it will keep, refrigerated for at least a week.

Mortar & Pestle
Add the garlic and the salt and pound until smooth.  Add the pine nuts and grind, then add half the basil and grind to a paste.  Add the rest of the basil and grind till smooth.  Now, whisk in the oil with a wire whisk.  Transfer to a bowl, and the parmigiano and beat the cheese in using a wooden spoon. Add the butter and beat the mixture until it is smooth.  Cover and set aside.  At this point you can refrigerate the pesto and it will keep, refrigerated for at least a week.

To Serve:
Serve over fettuccine or penne pasta. 
While your pasta is cooking, add two tablespoon of the cooking water to a bowl large enough to hold the pasta.  Stir in the pesto and the butter and stir vigorously with a wooden spoon.  When the pasta is cooked, drain very briefly (don't allow to dry) and add to the bowl with the pesto, toss to coat evenly.