Heat the stock in a saucepan and add the mushrooms, bamboo shoots, vinegar, soy sauce, sugar, ginger and chilli garlic sauce. Simmer for 3-4 minutes, then reduce the heat to low.
In a small bowl, mix the corn flour with 4 tablespoons of water and stir until smooth, then add to the pan. The soup will slowly thicken.
Add the tofu and sesame oil.
Swirl the soup so there is some movement in the pan. Drizzle in the eggs from a height to create ribbons, then turn off the heat.
Add the salt and pepper, then taste; if you want it more sour add rice vinegar, ad if you like it more spicy add in more chilli-garlic sauce. The balance of this dish is down to personal taste.
Before serving, sprinkle with the spring onions and red chilli.