Wash and dry produce.

Thinly slice scallions, separating whites from greens.

Heat a large drizzle of oil in a medium pot over medium-high heat. Add scallion whites and bok choy and napa cabbage; cook, stirring occasionally, until veggies are browned and softened, 3-5 minutes. Season with salt and pepper.

Transfer to a plate.

Heat a drizzle of oil in pot used for veggies over medium-high heat. Add beef*; cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Season with garlic powder, salt, and pepper.

Transfer to a plate.

To pot used for beef, add Szechuan paste, Sriracha, peanut butter, half the soy sauce, 3 cups water, and 1 tsp sugar (5½ cups water and 2 tsp sugar for 4 servings). Bring to a boil, then reduce heat to low; whisk until everything is thoroughly combined. Cook, stirring occasionally, until slightly thickened, 2-4 minutes.

Taste and add as much remaining soy sauce as you like. Taste and season with salt and pepper if desired.

Increase heat under pot with broth to medium-high. Bring to a boil. Once boiling, add noodles to pot, using tongs to break noodles apart. Cook until tender, 1-2 minutes.

Divide broth and noodles between bowls. Top with veggies, beef, scallion greens, and sesame seeds and serve.