Put the brown sugar in an airtight container
Add a slice of bread to the container
Add a few marshmallows to the container
Add a damp paper towel in a sealed bag to the container
Add a terra cotta brown sugar saver soaked in water
Microwave the sugar with a damp paper towel for a few seconds
Break up clumps with a fork or spoon
Store the sugar in a cool, dry place
Reseal the container tightly after each use