Drain and gently press the tofu (wrapped in a paper or tea towel) to remove excess moisture. Cut into triangular slices about ¼ inch (6mm) thick.
In a bowl, drizzle the soy sauce over the tofu, add salt and pepper and briefly stir. Then add the cornstarch and stir to evenly coat the tofu.
Heat up vegetable oil in large frying pan on medium-high to high heat and fry the tofu on both sides until crispy and golden brown. Remove tofu from the pan and set aside.
Sweet Chili Sauce
Add more vegetable oil to the hot pan if necessary. Fry the sliced red pepper for two minutes on medium-high heat, stirring frequently.
Reduce heat to medium and add sesame oil (if using), the white/yellow part of the spring onions, garlic and chilli flakes. Saute for 1 minute while stirring.
Add the water, vinegar, sugar and stock powder. Bring to a gentle simmer and stir to dissolve the sugar.
Stir together cornstarch and an equal amount of water to make a slurry. Stir the slurry into the sauce, and keep stirring gently until the sauce thickens up. Remove from heat or keep warm covered on very low heat until ready to serve.
When ready to serve, place the fried tofu back in the pan with the sauce. Sprinkle in chopped spring onion greens and stir to coat the tofu in sauce.Serve on noodles, rice, or another side of your choice.
Notes
Chilli flakes / red pepper flakes
The heat level of chilli flakes (called red pepper flakes in the US) in the varies widely, depending on which type chilli pepper they are made from. For us, mild to medium chilli flakes are perfect for this recipe, as they provide a lot of pepper flavour while keeping the heat kick to a tolerable level.How hot chilli flakes are is not always obvious from the product label. In our experience in the UK, most commercial chilli flakes found in supermarkets fall into a range from mild to medium, which work well for us in this recipe. Specialty and high quality brands can be very spicy though. So try around and find chilli flakes that suit your taste.Also, find out how different types of chillies compare in heat - useful if you know the name of the chilli pepper you are dealing with.You can also decrease or increase the amount of chilli flakes to suit your heat preference.