Cut the beancurd into 2cm cubes.

Steep the beancurd in very hot or gently simmering, lightly salted water.

Slice the leeks or spring onions at a steep angle into thin 'horse-ear' slices.

Season the wok.

Add groundnut oil and heat over a high flame until smoking.

Add the minced beef and stir-fry until it is crispy and a little brown, but not yet dry.

Turn the heat down to medium.

Add the Sichuanese chili bean paste and stir-fry for about 30 seconds, until the oil is a rich red color.

Add the black fermented beans and ground Sichuanese chilies and stir-fry for another 20-30 seconds until they are both fragrant and the chilies have added their color to the oil.

Pour in the stock, stir well and add the drained beancurd.

Mix it in gently by pushing the back of your ladle or wok scoop gently from the edges to the center of the wok - do not stir or the beancurd may break up.

Season with the sugar, soy sauce and salt to taste.

Simmer for about 5 minutes, until the beancurd has absorbed the flavors of the sauce.

Add the leeks or spring onions and gently stir in.

When they are just cooked, add the potato flour mixture in two or three stages, mixing well, until the sauce has thickened enough to cling glossily to the meat and beancurd. Don't add more than you need.

Pour everything into a deep bowl.

Scatter with the ground Sichuan pepper and serve.