Gently prick a few holes in the tofu with
a toothpick (this will help the marinade to
soak into it, giving better flavour), then
cut into bite-size cubes.
Mix the marinade ingredients together
in a bowl and toss in the tofu pieces.
Set aside to marinate for 10-15 mins.
Heat a wok over high heat and add half
the groundnut oil. When the oil starts to
smoke, add the ginger slices and stir-fry
for a few secs. Add the pak choy leaves
and stir-fry for 1-2 mins. Add a small
splash of water to create some steam
and cook for 2 mins more. When the
leaves have wilted and the stems are
cooked but still a little crunchy, season
with salt and transfer to a serving dish.
Rinse the wok under cold water, then
reheat it and add the remaining oil. When
it starts to smoke, add the tofu pieces
(retaining the marinade liquid) and stir-fry
for 5-10 mins. Take care not to break up
the tofu as you toss it to get it browned
evenly on all sides. Season with the rice
wine and rice vinegar. Add the remaining
marinade liquid, bring to the bubble and
let the liquid reduce. Sprinkle over the
chilli flakes and toss well. Spoon onto
the pak choy and serve immediately
with jasmine rice, if you like.