Spaghetti Aglio e Olio with Shrimp

Cook's Illustrated. Basically another simple shrimp in garlic oil over spaghetti recipe, which I do quite often. This one uses two lbs shrimp for one lb of pasta which is twice what I do.

Ingredients

3/4 cup extra-virgin olive oil
2 pounds shell-on jumbo shrimp (16 to 20 per pound), peeled, deveined, and cut into 1-inch pieces, shells reserved and chopped coarse
4 quarts water
1 pound spaghetti
2 tablespoons plus 1 teaspoon kosher salt, divided
6 garlic cloves, chopped fine
1 teaspoon red pepper flakes
1 cup fresh parsley, chopped fine
1 tablespoon lemon juice

Instructions

1. Heat oil in Dutch oven over medium-high heat until shimmering. Add shrimp shells and reduce heat to medium. Cook, stirring occasionally, until shells turn deep orange and oil is rust-colored and aromatic, 8 to 10 minutes. Strain oil through fine-mesh strainer into medium bowl, pressing on shrimp shells with rubber spatula to extract as much oil as possible; discard shells. Wipe pot clean with paper towels. Set aside 2 tablespoons infused oil and return remaining oil to pot.

2. Cook pasta according to directions. Drain, reserving 1/2 cup cooking water.

3. Meanwhile, add garlic, pepper flakes, and 1 teaspoon salt to Dutch oven and cook over low heat, stirring occasionally, until oil begins to gently foam and garlic turns pale golden, about 6 minutes. Add shrimp and season lightly with salt. Increase heat to medium and cook, stirring frequently, until shrimp begin to turn pink and opaque, 3 to 4 minutes. Add pasta and reserved cooking water and cook for 1 minute, stirring frequently to evenly coat pasta. Off heat, stir in parsley and lemon juice and season with salt to taste. Divide pasta among bowls and drizzle with reserved oil. Serve.