Slice the tofu into 1 cm thick square pieces and coat each piece lightly in the seasoned plain flour.
Heat a frying pan with oil over medium heat. Pan fry the tofu for about 4 minutes on each side until golden and crispy. Remove from the pan and set aside.
In a separate hot pan, add a little oil and half of the chopped garlic. Let it cook for about 30 seconds until fragrant.
Add the pak choi and 1 tablespoon of water. Cover with a lid and cook on medium heat for about 3 minutes until tender. Sprinkle with salt and set aside.
In a small bowl, mix together the oyster sauce, sugar, cornstarch, and cold water to make the sauce. Set aside.
Heat oil in a pan and add the mixed mushrooms. Stir fry for about 2 minutes.
Add the remaining garlic and continue to stir fry for another 2 minutes until the mushrooms soften.
Lower the heat and pour in the prepared sauce, stirring until it thickens slightly.
Add the crispy tofu to the pan and let it simmer in the sauce for 2 to 3 minutes.
To Serve
Arrange the pak choi around the edge of the plate.
Spoon half of the mushroom mixture into the centre, place the tofu on top, then add the remaining mushrooms over the tofu.
Garnish with chopped scallion.
