Gula Jawa, also known as Gula Merah, or red sugar, is one of the most severely misinterpreted ingredients in the West. This is a dense sugar derived from the Palmyra Palm but is extremely different from palm sugars typically sold in Western markets. While the Western varieties of palm sugar are also hard and dense, they are a light to dark brown color without the moistness of Gula Jawa.
Gula Jawa has an earthy aroma and deep sweetness with a color closely resembling molasses. In Asian markets in the West, I’ve only encountered one type of Indonesian Gula Jawa sold and those are in cylindrical shapes covered in white plastic wrap with the words “Gula Jawa” printed on the packaging. This wonderfully rich and full bodied sugar is unique to Indonesia and its flavors and moist, crumbly texture has no imitators.
When recipes call for Gula Jawa, it is best not to substitute. These days most Asian markets carry it along with online Asian grocery stores that widely offer this unusual ingredient. When absolutely necessary, substitute with dense, tightly packed brown sugar.