Start by heating oil in a large pot and adding sliced shallots and scallion whites. Cook them until soft and slightly golden to build a flavorful base. This step is important because it sets the tone for the entire soup. The aroma should become slightly sweet and inviting.
Add sliced mushrooms and sauté until they release moisture and soften. Then add shrimp and cook just until they turn pink and tender. Avoid overcooking as shrimp can become rubbery very quickly.
Mix in fresh ginger, garlic, and chili paste, letting them cook briefly. This releases their natural oils and intensifies the flavor. The fragrance at this stage becomes bold and slightly spicy.
Pour in vegetable broth, soy sauce, and rice vinegar, then bring everything to a gentle boil. Reduce heat and let it simmer for about 10 minutes. This allows all the ingredients to blend into a balanced, savory broth.
Mix cornstarch with water to create a slurry and slowly stir it into the soup. Let it cook until the broth slightly thickens and becomes glossy. It should feel light, not overly thick.
Turn off the heat and slowly drizzle in the beaten egg while stirring gently. This creates delicate egg strands similar to egg drop soup. It adds texture and richness without heaviness.
Taste the soup and adjust with salt and pepper if needed. Serve hot and garnish with scallions, sesame oil, or chili flakes. Each bowl should look vibrant and inviting.