In a food processor, combine mint leaves, garlic, grated cheese and pistachio. Process while drizzling in the olive oil. Process till smooth, about 1-2 minutes. Set aside.
Cook the Shells in salted boiling water until al Dente. Set aside.
In a large sautï¿½ pan, add the pesto and thawed peas and heat on a medium flame for 2-3 minutes.
Add the peas and the ricotta and mix until well combined.
Add in the shells and toss together until pasta is well coated.
Add some extra grated cheese and serve.