Bring a large pot of salted water to a boil and cook the conchiglioni until al dente, about 10-12 minutes, then drain.

Blanch the fresh petits pois in boiling water for 1-2 minutes, until bright green, then drain and rinse.

Combine ricotta, grated pecorino, lemon zest, olive oil, salt, and pepper in a bowl; fold in a handful of cooked peas.

Stuff the cooked conchiglioni with the ricotta mixture, about a tablespoon per shell.

Arrange the stuffed shells on a platter, drizzle with olive oil and lemon juice, sprinkle with pepper and fresh mint.

Top with radish pesto if desired before serving.