Cook the pasta. Drain. On a large tray, place the shells open side up.
In a large skillet, melt the butter over medium heat. Add the peas and asparagus. Season with salt and pepper. Cook for 3 - 4 minutes and set aside.
In a medium bowl, add the ricotta, pecorino Romano, lemon zest, salt, and pepper. Stir to combine. Stuff each shell with the ricotta mixture.
Arrange the shells on a serving platter. Top with the peas and asparagus. Drizzle with lemon juice, olive oil, and basil pesto. Serve topped with fresh basil leaves.
