1/4 cup Molasses
For every 1 cup sugar add 1/4 cup of molasses and pulse in the food processor.
If you like light brown sugar use half the amount of molasses, but I am a dark brown sugar girl.
Pulse till there isn't any lumps of molasses left or any white sugar left.
Then store in an air tight container.
My kids thought brown sugar was from a different plant so we sat down and made brown sugar together. I used a spoon (it gets out frustration and it gets some of my physical therapy done at the same time) and just paddled it down until it came out right so everyone would get a turn. A food processor is faster, and less messy.