Step 1

Place beef bones in a large Dutch oven or other heavy pot; pour in cold water to cover. Bring to a boil, then reduce heat to medium-low and cook 20 minutes. Drain bones in a colander (blanching the bones and discarding the liquid yields a clearer, tastier final broth). Rinse and wipe out pot; set aside.

Step 2

Toast star anise, Sichuan peppercorns, and 15 dried chiles in a dry small skillet over medium heat, tossing often, until fragrant and peppercorns are beginning to crackle, about 2 minutes. Transfer spices to a plate and let cool.

Step 3

Heat oil in reserved pot over high. Cook bean paste, stirring constantly, until fragrant and slightly darkened in color, about 2 minutes. Add onions, shallots, scallions, garlic, and ginger. Cook, still stirring, until onions are softened, about 5 minutes. Pour in wine; cook, stirring and scraping up any browned bits, until combined, about 30 seconds.

Step 4

Return bones to pot; add toasted spices, rock sugar, and soy sauce. Pour in 13 cups cold water and bring to a boil. Reduce heat to medium-low; cover pot and cook, adjusting heat as needed to maintain a gentle boil, 4 hours.

Step 5

Using a fine-mesh sieve, scoop out solids from broth. Pick out any meat and set aside in a small bowl for serving if desired; discard remaining solids. Stir 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt into broth; taste and season with more salt if needed. Top with more dried chiles.Do ahead: Broth (without topping) can be made 3 days ahead. Let cool; cover and chill, or freeze up to 3 months.