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.
Add the ground pea mixture to the skillet along with remaining chicken stock to thin it out, add the parsley leaves and the reserved box of peas. Add the cooked pasta shells, toss to combine and serve.