Wash and dry produce.

Trim and thinly slice scallions, separating whites from greens. Trim and discard woody ends from baby broccoli. Cut into 1-inch-long pieces.

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

Turn off heat; transfer to a plate.

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

Turn off heat; 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. 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 apart. Cook until tender, 1-2 minutes.

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