Thai soup can taste almost electric when it is right. One spoonful is bright with lime, warm with chiles, savory with fish sauce, fragrant with lemongrass, and still somehow clean enough to make room for the next bite.

A single habanero can change a pot of soup from mild and familiar to bright, fruity, and thrilling. The trick is knowing how to cook it so the heat supports the broth instead of taking over the bowl.