Pesto is to Italian cooking what coriander chutney is to Indian cooking. It has freshness from the basil, spice from the garlic and texture from the nuts and cheese. Olive oil makes it a perfect emulsion to have in as many ways as you want. Pesto is originally made from pine nuts but I use walnuts in mine, you can use either. Also pesto has pecorino romano in equal proportion to parmesan but I just use Parmesan as I have that on hand. You can use half parmesan and half pecorino if you have both the cheeses. Finally lemon juice - it adds freshness to the pesto and helps keep the bright green color of the pesto. But add it only if you are using the pesto on the same day.
2 cups fresh basil leaves
2 cloves garlic
3-4 tablespoons walnuts
1/2 cup olive oil
1/4 cup grated Parmesan
1 tablespoon lemon juice- if using the pesto the same day
Place the garlic, basil and salt in a blender. Blend to make a paste. Add the walnuts and cheese and blend while pouring the olive oil slowly in a stream till it is creamy. Serve in a variety of ways - here is one.