Rinse 150 g dried chickpeas, cover with water and refrigerate at least 8 hours until they crush easily under finger pressure. Drain and blend with 400 g fresh water for 2 minutes until completely smooth. Strain through a fine cheesecloth or nut milk bag, squeezing hard, to get a grit-free chickpea milk.

Pour the milk into a heavy-bottomed saucepan over medium-low heat. Bring just to a boil, then keep it bubbling gently for a few more minutes, whisking nonstop along the bottom and corners. It is ready when it thickens enough to coat the whisk.

Pour into a lightly oiled or lined container and smooth the top. Cool, then refrigerate at least 3 hours (overnight gives a firmer block). Turn out onto a board - it should hold an edge when cut.

Cut into even 2 cm cubes, trimming the rounded edges first. Pat dry with paper towel, then dust lightly all over with cornstarch and shake off the excess in a sieve.

Heat oil to about 160C and fry the cubes in batches until set and pale gold; lift out to drain. Raise the oil to about 180C and fry a second time, 30-60 seconds, until deeply golden and crisp. Drain on a rack.

Combine chili powder, sesame seeds, ground cumin and cilantro in a heatproof bowl. Pour a little hot oil over them to bloom the aromatics, then stir in soy sauce, brown sugar, black vinegar, chili oil, fermented tofu liquid and salt. Pour over the hot fried cubes, fold gently to coat, and serve immediately.