Spinach Pesto Penne with Shrimp and Peas

In a large pot of salted boiling water, cook pasta until al dente. Drain, reserving 1 cup pasta water, and return to pot. Meanwhile, make pesto: In a small food processor fitted with a metal blade, pulse spinach, basil, and 1/3 olive oil until combined. Add Parmesan, pine nuts or almonds, and garlic and season with salt and pepper. In a large skillet over medium heat, heat remaining tablespoon olive oil. Add shrimp and cook until pink, 3 to 4 minutes. Add pasta, pesto, and peas to skillet and toss until completely combined. Stir in 1/4 cup pasta water and stir until creamy. Sprinkle with Parmesan and chili flakes (if using).