Preheat a small frying pan over medium-high heat. Once the pan is hot (holding your palm close to the base, you should feel the heat within 5 seconds), break up the cinnamon sticks into smaller pieces for an even toast and throw them in the pan. Toast, stirring constantly or shaking the pan very often, until they darken further and smell incredibly fragrant, 1 to 2 minutes. Transfer them to a spice grinder (or clean coffee grinder), and allow the pieces to cool, about 5 minutes. Pulverise the cinnamon to the texture of finely ground black pepper.
Combine the cinnamon, curry powder, garlic and ginger in a large bowl; add the prawns and toss to coat. Refrigerate, covered, for at least 30 minutes or as long as overnight.
Heat the oil in a large frying pan over medium-high heat. Once the oil appears to shimmer, add the mustard seeds, cover and cook until the seeds have stopped popping, about 30 seconds. Immediately add the prawns in a single layer and sear them for about 30 seconds on each side.
Shake the coconut milk well and pour it in. Add the curry leaves, peppercorns and salt. Bring the curry to a boil and continue to cook until the prawns curl and turn salmon in colour, 3 to 5 minutes. Using a slotted spoon, transfer the prawns to a serving platter. Keep warm.
Continue to cook the sauce, uncovered, stirring occasionally, until it has thickened, 2 to 4 minutes. Spoon the sauce over the prawns and serve.
Never buy ground cinnamon as the oils in it dissipate in aroma and flavour. You are far better off grinding the whole sticks just before use.
Fresh curry leaves provide a mild citrusy flavour and intense aroma. Remove the leaves from the stem by sliding your fingers down the stem.
(Excerpted from On the Curry Trail: Chasing the Flavor That Seduced the World by Raghavan Iyer. Workman Publishing © 2023.)
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