Prepare lemongrass by cutting into 1 1/2 inch lengths.

Tear kaffir lime leaves off the center spine.

Slice shallots.

Prepare Thai bird's eye chili peppers.

Peel and devein shrimp, leaving tails on.

Place water in a 3-quart saucepan.

Add lemongrass, lime leaves, and shallots to the water.

Bring the mixture to a boil.

Add chili peppers and shrimp to the boiling water.

Cook for 2 minutes.

Add enoki (straw) mushrooms, lime juice, fish sauce, and salt.

Add tomato wedges and cook until heated but still firm.

Pour the soup into a serving bowl.

Top with pak chee farang and cilantro leaves.