1. Peel the shrimp and put them back in the fridge. Add the scales and heads to a large pot. Also add the dried chillies, sliced lime, the garlic cloves, lemongrass, fresh ginger and cold water.

2. Place the pot over high heat and bring it to a boil. Then turn the heat low, cover the pan and simmer the shrimp scales in the broth for 20 minutes. Then turn the heat off and place the sieve over another large pan. Pour the broth and ingredients in it.

3. Remove the red chili peppers and keep them aside. Stir the cooked scales and heads to get as much of the flavorful shrimp broth out. Then discard what’s left. Add the onion the broth as well as the red chili peppers and bring it to a gentle simmer again. Cook for about 6 to 8 minutes until the onion starts to soften.

4. Slice the mushrooms and tomatoes in bite size bits. Add them to the soup together with the peeled raw shrimp. Season with half of the fish sauce, half of the lime juice, a little hot chili sauce and half of the palm sugar.

5. Stir the soup and cook for another 2 minutes until the mushrooms are warmed through. Then check the seasoning and add extra hot chili sauce, palm sugar, fish sauce or lime juice to taste. Stir in the chopped cilantro.

6. Scoop the hot and sour shrimp soup into large bowls and serve hot.