1/4 c. olive oil (or cooking oil)
1/2 c. chopped nuts (walnut, almonds, or pine nuts)
2 c. firmly packed fresh basil leaves
1/2 c. grated Parmesan or Romano cheese
4 cloves garlic, peeled and quartered
1/4 t. salt
If using a food processor, combine oil, nuts, basil, cheese, garlic, pepper and salt, processing until nearly smooth. If you're using a blender, it will be easiest to first chop the basil and nuts before adding them to the mixture.
See? It's that easy.
I like to make a huge batch and freeze individual portions. Pesto's optimal life in the freezer is 3 months.