Bring a large pot of salted water to a boil. Wash and dry produce.

Trim and thinly slice scallions, separating whites from greens. Trim and halve Brussels sprouts lengthwise; lay flat, then thinly slice crosswise into shreds. Zest and quarter lemon.

Once water is boiling, add linguine to pot. Cook, stirring occasionally, until al dente, 9-11 minutes.

Reserve 1½ cups pasta cooking water (2 cups for 4 servings), then drain. (Keep empty pot handy for step 4.)

Meanwhile, melt 1 TBSP plain butter (2 TBSP for 4) in a large pan over medium-high heat. Add panko and cook, stirring, until golden and toasted, 2-3 minutes. Stir in scallion whites and season with salt and pepper. Turn off heat; transfer to a small bowl. Wipe out pan.

Heat a large drizzle of olive oil in same pan over medium-high heat. Add Brussels sprouts and season with salt and pepper. Cook, stirring occasionally, until bright green and slightly softened, 4-6 minutes.

Stir in a pinch of chili flakes if desired; cook for 30 seconds more. Turn off heat.

Once linguine is drained, heat empty pot over medium heat. Add cheese roux and 1 cup reserved pasta cooking water (1½ cups for 4 servings); whisk to combine. Cook, whisking, until slightly thickened, 2-3 minutes.

Reduce heat to medium low and whisk in cream cheese until melted and combined.

Add drained linguine, Brussels sprouts, garlic herb butter, Parmesan, scallion greens, half the lemon zest, and a big squeeze of lemon juice to pot with sauce. Cook, tossing, until butter has melted and pasta is coated in a creamy sauce, about 1 minute. TIP: If needed, stir in more reserved pasta cooking water a splash at a time.

Taste and season with salt and pepper. Add more lemon juice if desired.

Divide pasta between bowls. Top with panko and remaining lemon zest to taste. Sprinkle with remaining chili flakes if desired. Serve with any remaining lemon wedges on the side.