Dry toast all the Sichuan peppercorns in a wok or frying pan for 1 minute on low heat, then transfer to a small mortar (pestle and mortar, the bowl).
Heat the oil in the same wok or frying pan over medium-high heat and fry the dried chillies for one minute.
Transfer the oil and chillies into a medium sized heatproof bowl and add the chilli flakes and roughly about 10 of the toasted Sichuan peppercorns (about ¼ tsp). Leave to infuse while you get everything else ready.
Marinate the Tofu
Cut up the tofu into cubes measuring about 2.5cm/1″. If you are using silken tofu as the traditional recipe calls for, it is going to be prone to breaking up, so be gentle. It's probably going to come apart in 2-3 pieces as you are getting it our of the packaging. Don't worry too much about it. Cut it in cubes as much as possible.Place the tofu cubes into a wide, flat bowl or plate. Piling the cubes on top of each other will only encourage them to break up easily from the weight.
Grate the ginger and place in a small bowl.
Add the sesame oil, soy sauce and Shaoxing wine to the bowl and stir to mix well.
Pour this marinade all over the tofu cubes. Then gently, just shake the plate slightly to allow the marinade to cover as much of the tofu as possible. Leave aside while you get the other ingredients ready.
Other Prep Work
Lightly crush the sichuan peppercorns with a pestle and mortar.
Slice your shiitake and set aside.
Finely chop your garlic and ginger. Slice the spring onions into about 1cm (½") lengths. Then separate the green and white parts. We cook the white, and use the green as garnish.
Heat the 2 Tbsp of vegetable oil in a wok or large, deep frying pan on medium heat and fry the sichuan peppercorns, the garlic, ginger and white sliced spring onions (scallions) for 30 seconds.
Increase the heat to medium-high and add the shiitake, frying for about 1 minute.
Add the doubanjiang and wine and stir to mix.
Add the water, stir and bring back to simmering point.
Stir the cornflour and water and drizzle this into the wok, stirring, while doing so. Cook for 30 seconds, to allow the sauce to thicken.
Add the tofu cubes, and VERY carefully stir the tofu and the sauce, being careful to break up as little of the tofu as possible. But don’t fret too much, if it’s your first time. Let the tofu cook for 3 minutes.
While the tofu is cooking, strain the chilli oil you made earlier into a clean cup or bowl. Drizzle some of the chilli oil all over, however much or however little you like. I usually use 2 Tbsp of it and keep the other 2 Tbsp, covered, in the fridge, to use later. It'll keep for a week. (Image shows a previous Sichuan oil, with chilli powder, recipe for that here).
Take off heat, scatter the green spring onions (scallions) all over and serve immediately.
Notes
The nutritional information includes all 4 Tbsp of the chilli oil.