Place the brown sugar in a microwave-safe bowl.
Microwave on low power for 10–20 seconds.
Stir and break up the sugar.
Repeat in 10–20 second intervals until soft.
If it’s still hard, sprinkle a few drops of water over the surface.
Stir, then microwave again in short intervals.
Alternatively, place the brown sugar in an airtight container with a slice of fresh bread or a damp paper towel.
Seal the container and let it sit for 4–24 hours.
For oven method, spread sugar on a baking sheet in a thin layer.
Bake at 250°F (120°C) for 3–5 minutes, stirring once.
Cool fully before using.