Smash lemongrass, garlic, and galangal. Tear lime leaves and chop chilies.
Cut mushrooms, tomato, and onion.
Bring broth to a boil with lemongrass, garlic, galangal, lime leaves, and chilies.
Add tomato and onion, simmer for 2-3 minutes.
Add shrimp and simmer for 1-2 minutes.
Stir in sugar, fish sauce, and lime juice.
For creamy soup, stir in evaporated milk and Thai chili paste.
Garnish with cilantro and serve.