Cuisine is regional, but methods of cooking are not. If you compare two different cuisines, you will see similarities in many dishes. The ingredients used of course will be locally available ones, but methods of preparation and the courses of meals have many similarities. It could be due to foreign influence, but not always.
Pesto is one such preparation that can be compared to our South Indian Chutney. Pesto has nuts and chutney has roasted dal /lentils. Pesto uses Italian herbs and chutney uses Cilantro or mint. The reason for adding olive oil to pesto is to make it shelf stable. If you are using pesto immediately, there is no harm in using water. We use tamarind in chutney as acid and pesto uses lemon juice as acid part of it. I made an Indian version of pesto and made pasta out of it. This is one of the pasta my relatives and friends enjoy very much.
One year back - Banana Oatmeal Bread
Walnuts - 1/2 cup
Green chillies - 6 or to taste (This itself makes it pretty spicy)
Cilantro / Coriander leaves - 2 cups packed (about one big bunch)
Garlic - 3 pods
Olive oil - 4 TBSP
Black pepper - 1/2 TBSP (See Notes)
Lime juice - from 1/2 a lime or 1 TBSP (Could use lemon juice too)
In a skillet, toast the walnuts till nice smell comes out of them. About 4 - 5 minutes depending on the how high the heat is. Set aside. In a food processor or blender, combine all the ingredients excluding olive oil. Start the food processor while slowing drizzling the olive oil. Run it till you get a smooth paste. You are done making pesto. You could add salt, but I prefer to add it to the pasta when I cook since I use over salted pasta water to thin down the sauce.
Assembling the pasta:
Here is how I made pasta using this pesto. I used about 2 cups of penne. 2 carrots peeled and sliced, 1 cup of frozen green peas and 2 red onions cut into chunks. Bring a big pot of water to a boil. Salt generously. Add peas and carrots and let them cook for about 3 - 4 minutes. Now add the penne to the same pot and let them cook till al-dente. Meanwhile, heat 1 - 2 TBSP of olive oil. Saute onions. When onions are cooked, add the cooked pasta and vegetables to it, pesto and thin down using pasta water. Only after you add the pasta water, add salt if necessary. Let it all simmer for 3 - 4 minutes and then turn off the heat. This is best served immediately just like any other pasta, but will heat up beautifully. If you are planning to save some, add more of the pasta water to make it very saucy so that it doesn't dry up. You can use your favorite vegetables and the quantity of them can be varied too.
You could add black pepper to the pasta when you cook. In that case, omit black pepper while making pesto. Black pepper and green chillies hit the palate in different places. That is the reason for adding both.