Gently wash the basil in cold water and pat dry with a towel. Crush one clove of garlic in the mortar and add some basil (30 leaves per clove), and then a sprinkle of salt. In a gentle circular motion, use the mortar to tear the basil until it turns into a bright green oily liquid. Repeat this process until all the basil and two cloves of garlic are added. Add the pine nuts and gently crush them into the mixture. Next, add the cheese. When the cheese is mixed in, slowly drizzle in the olive oil and mix together. At this point, the pesto is ready to use.
Prepare the Shrimp
Clean and wash the shrimp. Cut into bite-sized pieces. Mince the one remaining clove of garlic. In a large skillet over medium heat, saute the garlic in olive oil until lightly golden. Add the shrimp and cook for a few minutes until pink. Remove from heat.
Bring a large pot of salted water to a boil. Cook the pasta until al dente, retaining some of the cooking water. Drain the pasta and place it in a serving bowl. Slowly mix in the pesto sauce and then the shrimp, adding a few tablespoons of the cooking water if it looks dry.