Cut the tofu into approx. 1 cm cubes, place in a deep-sided bowl. Pour over the soy sauce, cover and leave to marinate in the fridge for approx. 30 mins.
Slice the garlic, dice the pepper, cut the spring onions into thin strips and slice the green part into rings. Heat the oil and sauté the garlic, onions and pepper for approx. 3 mins. Add the stock and bring to the boil.
Reduce the heat and simmer the soup for approx. 5 mins. on a low heat. Add the tofu with the marinade, bean sprouts and green part of the spring onions, gently heat, season the soup and serve. Serve with white bread.