Place a large pot of water over high heat and bring to a boil. Add some salt and the pasta shells, and cook to al dente according to the package directions.
While the pasta is cooking, place a large non-stick skillet over medium-high heat, add EVOO. Add the pancetta and cook for about 5-6 minutes or until browned. Add the onions and garlic and cook for 1-2 minutes. Add the shrimp, season with salt and pepper and cook for about 2-3 minutes or they've turned pink and have curled up.
While the shrimp are cooking, place 1 box of the defrosted peas in a food processor along with the lemon juice, lemon zest, and chicken stock, puree until smooth.