Slice the firm tofu into bite-sized cubes, and thinly slice the shiitake mushrooms for optimum flavor. Whisk the eggs until well-beaten.

In a medium saucepan, pour in four cups of vegetable broth and bring to a gentle simmer over medium heat, about 5 minutes.

Stir in rice vinegar and white pepper, followed by soy sauce. Let the mixture simmer for another 2 minutes.

Mix cornstarch with cold water until smooth and pour into the simmering broth while continuously stirring.

Gently fold the cubed tofu and sliced mushrooms into the broth and allow them to cook together for about 5 minutes.

Reduce the heat to low and drizzle whisked eggs into the pot while stirring continuously to form silky strands.

Ladle the hot soup into bowls and optionally drizzle with sesame oil and sprinkle chili flakes before serving.