Cut the beef flank steak along the grain into two pieces. Then slice against the grain by tilting your knife to 45° and slicing the beef into 1/4" (1/2 cm) thick pieces. Transfer to a medium-sized bowl.

Add the marinade ingredients except the cornstarch. Gently use your hand to mix the beef until the ingredients are absorbed. Then add the cornstarch and mix again until the beef is evenly coated. Set aside to marinate for 15 minutes while preparing the rest of the ingredients.

Heat a medium-sized wok over medium heat with 2 tablespoons of oil until hot. Add the dried chilis and Sichuan peppercorns, turn to medium-low heat. Cook and stir until fragrant and darker, about 2 minutes. Transfer the spices to a plate to cool slightly, reserving the oil in the pan. Turn off the heat.

Add the fried spices into a small food processor or blender. Pulse until coarsely chopped. Set aside.

Reheat the same wok over medium heat until hot. Add the garlic, ginger, and scallions. Cook and stir until fragrant, 1 minute or so.

Add the doubanjiang. Stir for another 2 to 3 minutes. Turn to low heat if the paste starts to stick to the pan too much. You can also pour a bit of water into the pan to release the paste.

Pour in the Shaoxing wine and use a spatula to lift as much of the brown bits from the bottom as possible. Add the chicken stock and keep scraping the bottom.

Add the sugar and soy sauce. Cook over medium-high heat until brought to a boil. Reduce to a simmer and cook for 2 to 3 minutes. Use a mesh strainer to remove the solid spices and discard them. Taste the broth. It should be slightly salty by itself. Add chicken bouillon to adjust flavor if needed.

Prepare a large heat-proof bowl, enough to hold most of the broth, the vegetables, and the beef. (*Footnote 1)

Add the Chinese broccoli to the broth and blanch until cooked to your desired texture, about 2 minutes. Remove it from the broth and place it on the bottom of the big bowl.

Bring the broth back to a simmer. Cook the beef slices in two batches if needed so they don’t crowd the pan. Add the beef and immediately use a pair of chopsticks or tongs to stir and separate the pieces. Poach for a minute, or until the beef is just cooked through. Transfer the beef into the big serving bowl, on top of the Chinese broccoli.

Bring the broth to a boil again. Stir to fully dissolve the cornstarch slurry and pour it into the broth, stirring constantly. Cook for 1 minute, until the broth is slightly thickened. Then pour the broth into the serving bowl, until the beef slices are mostly covered. Set aside the remaining broth if there is any left. (*Footnote 1)

Spread the prepared topping spices - the fried and ground up chili peppers and Sichuan peppercorn, over the broth. Spread out the sliced scallions and the grated garlic.

Heat the remaining 1/4 cup oil over medium heat in a small pot or saucepan until just smoking. Carefully drizzle the spices over the serving dish. The oil will spatter a bit but shouldn’t cause a mess. Serve hot as a main dish.