Bring a pot of salted water to a boil. Add the linguine and cook until just tender, 8 to 10 minutes. Drain, reserving ¾ cup of the cooking water. While the water heats, start the leeks.

• Trim the root ends and any dark green leaves from the leeks; cut them in half lengthwise, then crosswise into ¼-inch-thick half-moons. Rinse.
• Finely chop enough garlic to measure 1½ teaspoons.

In a pan over medium-high heat, warm 2 tablespoons oil. Add the leeks and garlic and cook until the leeks have softened, 8 to 10 minutes. While they cook, prep the remaining ingredients.

• Strip the thyme leaves from the stems.
• Zest and juice the lemon.
• Strip the parsley leaves from the stems; finely chop the leaves.
• Coarsely chop the romaine heart.
• Season the shrimp generously with salt and pepper.

To the pan with the leek mixture, over medium-high heat, if using, pour in ¼ cup wine and cook until reduced slightly. Stir in the shrimp and reserved pasta cooking water. Add the linguine, thyme, lemon zest, and lemon juice, and toss to combine.
Cook until most of the liquid has been absorbed and the shrimp is cooked through, 2 to 3 minutes. Remove from the heat. Stir in the parsley and as much of the Marash chile flakes as you like. Season to taste with salt and pepper.

In a bowl, combine the vinegar and 1½ tablespoons oil. Add the romaine and Parmesan and toss. Season to taste with salt and pepper.

Transfer the scampi to individual bowls. Serve with the romaine salad on the side.