Sear the Prawns: Heat the vegetable oil in a large saucepan over high heat. Add the prawns and sear them on both sides until lightly golden. They do not need to be fully cooked through at this stage. Transfer the prawns to a plate.
Adjust the Heat: Reduce the heat to medium. If the saucepan looks dry, add a small amount of extra oil.
Cook the Aromatics: Add the finely grated garlic, ginger, and lemongrass. Sauté for about 20 seconds, until the garlic turns golden.
Add the Sugar and Fish Sauce: Stir in the brown sugar and fish sauce. Cook for about 30 seconds, stirring, until the mixture develops a caramel-like appearance.
Toast the Spices and Chilli Paste: Add the chilli paste, coriander powder, and curry powder. Stir continuously and cook for 30 seconds to combine the flavors.
Create the Coconut Broth: Pour in the chicken broth and coconut milk. Stir well and bring the mixture to a simmer.
Add the Lime and Prawns: Simmer the broth for 2 minutes. Stir in the lime zest, then return the seared prawns and any juices from the plate to the saucepan.
Finish the Soup: Cook for another 2 minutes, just until the prawns are reheated and finish cooking.
Prepare the Noodle Bowls: Divide the prepared fresh egg noodles among serving bowls.
Serve the Soup: Ladle the hot coconut broth and prawns over the noodles.
Add the Toppings: Top with bean sprouts and fresh coriander/cilantro. Add sliced red onion or green onion, fried Asian shallots, sliced red chilli, and extra chilli paste as desired.
Finish with Lime: Serve with lime wedges and squeeze fresh lime juice over the soup to taste before eating.
