Cut the pork tenderloin into 6 equal chunks, then bash them flat (1cm or just under ½") with a meat mallet.
Remove the stones from three of the plums and cut them into a 1cm (just under ½") dice.
Cut the shallot in half lengthways, then peel it and, then cut it into thin half-moon-shaped slices
Peel the garlic clove and slice it as finely as you can.
Heat half of the cooking oil in a small (24cm or 10") frying pan over a medium heat. When the oil is hot, add the star anise and the sliced shallot until it begins to soften.
Add the plums and sliced garlic, then cook for 5 minutes, stirring a couple of times.
Pour in the vegetable stock, soy sauce, vinegar, toasted sesame oil and honey. Stir to coat and reduce the temperature to low. Cook for 10 minutes.
Remove the star anise from the plums and transfer it to a blender and blitz to a smooth sauce, then pass it through a fine-mesh sieve back into the pan. Keep it warm on a low heat whilst you cook the meat.
Cut the remaining plum in half, then remove the stone and slice it into thin strips 2-3mm (⅛") thick.
Heat a large (30-35cm or 12-14") frying pan over a high heat and add the Szechuan pepper and toast it for 1-2 minutes, then grind it to a fine powder.
Season the pork slices with the Szechuan pepper and Chinese five-spice.
Heat the remaining oil in the pan that you toasted the Szechuan pepper in over a high heat. When the pan is hot, fry the pork medallions for 1 minute on each side.
Transfer the pork medallions to the sauce and return the pan to a high heat, add the plum slices and fry for 1 minute.