Made by boiling down sap collected from the cut stalks of immature flowers of the sugar, palmyra, or coconut palm, palm sugar was historically used in the south and center of Thailand, where palm trees are abundant. Less sweet and more complex in flavor than white cane sugar, palm sugar delivers hints of tartness, smoke, caramel, or butterscotch, depending on where and how it's produced. It keeps for a long time at room temperature, so it's easy to keep on hand for use.
Palm sugar comes in three forms. You may spot cellophane-wrapped, golden-yellow-to-medium-dark-brown cakes or mounds, which must be broken into pieces and shaved with a cleaver or knife; individual tablespoon-sized blocks that are packaged in tubs; or the softer version, with a texture akin to honey butter (but denser), packaged in jars and plastic tubs. Indian palm jaggery and other Southeast Asian palm sugars, like Malaysian gula melaka or Indonesian gula jawa, can be substituted in a pinch.