PREPARE THE PRAWNS
Peel and devein all 12 king prawns, keeping the shells and heads. Use a toothpick inserted under the dark vein about halfway along the prawn's back, gently lift and pull to draw the entire thread out in one piece. Rinse briefly under cold water.
Set the peeled, deveined prawns aside on a plate lined with paper towels. Reserve all shells and heads in a separate bowl.


BUILD THE BROTH
Heat 1 tablespoon oil in a medium saucepan over high heat. When the oil is shimmering, add the prawn shells and heads. Cook, pressing them down with a wooden spoon to release their oils, for 2–3 minutes until they turn deep pink-red and smell intensely fragrant.
Add the sliced shallot, ginger coins, lemongrass, chili, and lime leaves. Stir for 1 minute until the aromatics soften and become fragrant.
Add the grated jaggery and stir until it melts and begins to lightly caramelize around the shells, about 30 seconds. Jaggery is an unrefined cane sugar used across South and Southeast Asia that adds a rounded, toffee-like sweetness. Light brown sugar or palm sugar are acceptable substitutes.
Pour in the fish stock, scraping up any caramelized bits from the bottom of the pan. Bring to a boil, then reduce to a steady simmer. Cook for 10–12 minutes to extract maximum flavor from the shells and aromatics.
Strain the broth through a fine-mesh sieve set over a clean saucepan. Use the back of a ladle or a large spoon to press firmly on the solids, crushing the shells and squeezing the aromatics to extract every drop of liquid and flavor. The strained broth should be deeply aromatic and a rich amber-gold color. Discard the solids.
Return the strained broth to medium heat. Stir in the thick coconut cream, fish sauce, and lime juice. For the coconut cream, refrigerate a can of full-fat coconut milk overnight and skim the thick, solid cream from the top. Taste and adjust seasoning — it should be savory, fragrant, slightly sweet from the jaggery, with gentle chili warmth and bright lime acidity. Keep warm over low heat.


MAKE THE PRAWN TOAST
Place the 150 g raw prawns in a food processor with the egg white, garlic, ginger, lemongrass, soy sauce, sesame oil, white pepper, and salt. Pulse until you have a smooth, sticky paste — about 15–20 pulses. The egg white binds the mixture and helps the toast puff slightly when fried.
Using a round cutter (about 7.5 cm) or a sharp knife, cut rounds from the bread slices. You should get 2 rounds per slice, for 4 toasts total.
Mix the white and black sesame seeds together on a small plate.
Spread a generous, even layer of the prawn mixture onto one side of each bread round — about 6 mm thick, domed slightly in the center. Press the prawn side firmly into the sesame seed mixture to coat evenly.
Heat the vegetable oil in a small, deep skillet over medium heat to 170°C (340°F). Test by dropping a small piece of bread into the oil — it should sizzle immediately and turn golden within about 30 seconds.
Carefully lower the prawn toasts into the oil, prawn side down first. Fry for 1½–2 minutes until the sesame seeds are golden and the prawn mixture is set and lightly puffed. Flip and fry the bread side for 30–45 seconds until golden and crisp. Remove to a wire rack or paper towels. Season immediately with a tiny pinch of flaky salt.


COOK THE KING PRAWNS
Melt the butter in a large skillet over medium-high heat. When it foams and begins to smell nutty, season the deveined king prawns with salt and white pepper and add them in a single layer. Cook for 1–1½ minutes on the first side until golden. Flip and baste continuously — tilt the pan slightly and spoon the foaming butter over the prawns repeatedly as they finish cooking, another 1–1½ minutes. The prawns should be pink, curled, and just cooked through — bouncy to the touch, not rubbery. Remove from heat immediately.


ASSEMBLE AND SERVE
Ladle the warm coconut-lemongrass broth into two wide, shallow bowls. Arrange 6 seared king prawns in each bowl, nestled into the broth. Place 2 prawn toasts alongside the prawns, resting against the edge of the bowl or on a small side plate. Garnish with fresh cilantro leaves and sliced red chili. Serve with lime wedges on the side.