Start by preparing the aromatics. Peel and mince the ginger finely and transfer it to a bowl. Trim the stems from the serrano or jalapeño peppers, slice them into thin rounds, and add them to the bowl. Slice the scallions thinly, both the green and white parts, and finely chop the red onions. Grate the zest from the lime and add it to the same bowl, mixing everything together to create a fragrant base.

Prepare the lemongrass by trimming away the tough outer leaves until you have about 6 to 7 inches of the lower stalk. Halve each stalk lengthwise and lightly crush the base with the flat side of a knife to release its oils. Tie the stalks together securely with kitchen twine to make a bundle.

In a large Dutch oven or heavy-bottomed pot, heat the canola oil over medium heat until it begins to shimmer. Add the lemongrass bundle, the aromatic mixture from the bowl, and the anchovy fillets along with their packing oil. Stir frequently, breaking up the anchovies into small bits as they melt into the mixture. Cook for 8 to 10 minutes, or until the onions turn translucent, the scallions dull slightly, and the mixture takes on a light golden hue.

Meanwhile, dice the tomatoes into large chunks and set them aside. Cut the zested lime into wedges and keep them ready for serving.

Increase the heat to medium-high and add the diced tomatoes to the pot. Stir occasionally and let them cook for 8 to 10 minutes, until they soften, collapse, and their juices thicken into a rich, savory base. While the tomatoes cook down, rinse and dry your choice of greens—chile leaves, sweet potato leaves, or spinach. Clean the prawns thoroughly under cold water, trimming off the long antennae if necessary. For a cleaner presentation, you may slit the back of each prawn and remove the vein.

Pour in the coconut milk, followed by the salt and black pepper. Stir well to combine and bring the mixture to a gentle boil, stirring occasionally for 6 to 8 minutes. Once it begins to bubble, reduce the heat to maintain a low simmer. Allow it to cook for another 10 to 12 minutes, stirring occasionally, until the sauce thickens slightly and reduces by about one-fourth.

Add the cleaned prawns to the simmering coconut sauce. Stir to coat them evenly in the rich, aromatic mixture. Cover the pot and let the prawns simmer for 5 minutes. Uncover, stir, then cover again and continue cooking for about 2 minutes more, or until the prawns are pink, firm, and opaque throughout. Taste the sauce and adjust with additional salt and pepper as needed.

Turn off the heat. Add the prepared greens and, if desired, the extra sliced chili for added heat. Stir gently to combine, then cover the pot again. Let it sit for 2 minutes to allow the greens to wilt gently while retaining their vibrant green color. Remove and discard the lemongrass bundle before serving.

Serve the prawns and their luscious coconut sauce over a bed of steamed jasmine rice. Garnish with fresh lime wedges for a bright, citrusy finish that enhances every creamy, savory bite.