Add sugar to a medium bowl. Pour molasses over sugar. Use a fork to combine the molasses into the sugar. You can also use a whisk, wooden spoon or an electric mixer. I have even used a blender. But, in the end the fork is my favorite method.
Continue pressing fork into sugar until the molasses and brown sugar are fully combined and there are no molasses chunks left.
Store in a sealed resealable container. Use as needed.
Notes
For light brown sugar use 1 tablespoon molasses, for dark brown use 2 tablespoons molasses.