How Do You Soften Brown Sugar That Has Hardened. Petrini.elisa september 4, 2013 a chunk of apple will soften up an entire box of hardened brown sugar in a day or two If you need to use hard brown sugar immediately, preheat oven to 250˚ f.

How to soften powdered sugar: You do not want the edges or tops to brown at all. First, it's hard to measure properly since hard brown sugar has morphed.