Heat wok over medium-high heat with 1 tbsp oil until just smoking. Add beef, stir fry into small pieces. Remove and set aside when cooked through and starting to brown - don't over cook
Clean wok, return to heat until hot, add remaining 5 tbsp oil. Add doubanjiang, dou chi, and chili powder, stir frying until fragrant but be careful not to burn them
Add chicken stock, soy sauce, scallions, reserved beef, and tofu. Simmer for a few minutes, gently tossing the tofu with the sauce
Combine cornstarch and water in a small bowl, then add to the mapo tofu to thicken. Add peppercorn and serve