For the spicy shrimp and ground beef buns: Combine the shrimp and dried mushrooms in a bowl and pour 1 cup boiling water over to cover. Let stand at least 10 minutes, and then drain, reserving the liquid, and finely chop.
Heat a wok over medium-high heat and add the peanut oil. Add the shrimp, mushrooms, bacon and shallots and fry, stirring constantly, 1 to 2 minutes. Stir in the ground beef, breaking the meat up with a spatula and cooking until no longer pink, 3 to 4 minutes.
Add the bamboo shoots, jalapenos and green peppers and toss 1 to 2 minutes. Drizzle in about 1/2 cup of the mushroom soaking liquid along with the light soy sauce, dark soy sauce and rice wine and bring to a simmer. Stir in the cornstarch slurry and cook until thickened and glossy, about 1 minute. Season with the white pepper.
To serve, spoon about 1/2 cup of the mixture (depending on the bun size) onto each bun and garnish with the cornichons, a drizzle of chili oil, if using, and the cilantro. Sprinkle the peanuts with sugar, if using, over the top of each bao and serve immediately.