Rinse the jasmine rice under cold water until the water runs clear. Drain well in a wire mesh strainer.
Remove any dry external leaves from the lemongrass, cut it into 3 inch sections, and bash the lemongrass firmly with the side of a heavy cleaver or knife. -This will help the lemongrass to please its oils to the rice when cooked.
Heat the oil in a saucepan over medium heat. Add the lime leaves, lemongrass, and cardamom stirring for 30 seconds until fragrant.
Add the drained rice and stir for 2 minutes to coat evenly with the oil.
Pour in the coconut milk, water, salt, and sugar. Stir briefly to combine.
Bring to a gentle boil over medium-high heat, then reduce to low heat. Cover and simmer for 23-25 minutes.
Remove from heat and let sit, covered, for 10 minutes. Discard the lime leaves and lemongrass. Fluff the rice with a fork before serving.
Garnish with cilantro, coconut scallions, or Thai basil, if using. Serve warm.