Preheat your oven to 200°c/390°f (fan oven).
Take the 400g block of firm tofu and press all of the water out of it. Leave the tofu to sit in the tofu press for at least 10 minutes to ensure as much moisture has been removed as possible. (If you don't have a tofu press you can wrap the tofu in a kitchen towel and place a baking tray over the top. Then place whatever heavy items you have lying round in the kitchen. You can use cans, bags of sugar, whatever you have available.)
Once you're tofu has been pressed, slice the block into 1cm thick cubes. Add the cubes to a mixing bowl and cover with 1 tablespoon of flour, 1 tablespoon cornflour and 1 teaspoon of salt. Toss the tofu to ensure that the flour evenly covers the blocks.
Next pour 4 tablespoons of vegetable oil onto a large baking tray and place into the oven for 5 minutes. Once the oil is nice and hot, pour the tofu on the baking tray and toss the blocks in the oil before placing back in the oven for 30 -35 minutes until golden brown. Halfway through cooking turn the tofu to ensure even browning on all sides.
Whilst the tofu is in the oven cook the sweet and sour sauce. Heat 1 tablespoon of vegetable oil in a frying pan over a medium heat and toss in 4 cloves of diced garlic and 1 diced red chilli. Fry for around 3 minutes until the garlic is soft.
Now pour in the juice of 2 limes, 1/2 tablespoon rice wine vinegar, 2 tablespoons of soy sauce, 2 1/2 tablespoons of brown sugar and the 1 tablespoon of cornflour slurry. Cook until the sauce has thickened into a gloopy paste.
Pour in 200ml of vegetable stock and stir to combine. Then cook vigorously for 5 minutes until the sauce has become wonderfully thick.
Toss the sweet and sour sauce with the tofu and serve immediately. The tofu goes well with rice or noodles. I like to garnish the dish with some freshly sliced spring onions and a sprinkling of sesame seeds.