Step 1

Place noodles in a large saucepan or skillet and cover with room temperature tap water by 1 inch. Season lightly with salt. Bring to a boil over high heat and cook, stirring occasionally, until almost done (follow package directions for cook times). Drain all but 1 cup of water. Return to high heat and simmer until water is almost completely reduced.

Step 2

Meanwhile, combine crème fraîche, egg, cornstarch, and 1 tablespoon lemon juice in a medium bowl and whisk with a fork or whisk until homogenous.

Step 3

When noodles are cooked, add crème fraîche mixture to skillet and cook, stirring and tossing constantly, until sauce thickens and coats noodles. Season generously with black pepper and salt. Off heat, gently fold in tuna, peas, parsley, and remaining lemon juice until warmed through. Serve immediately drizzled with extra-virgin olive oil and sprinkled with crushed potato chips, if desired.