Combine the sugar and molasses in the mixing bowl or the bowl of your stand mixer.
Turn on the mixer or begin mixing to incorporate the molasses into the sugar.
The molasses will begin to clump up on top of the sugar. Use a spoon or spatula to press the molasses pieces into the side of the bowl.
Continue mixing like before until all of the molasses clumps have broken apart and fully integrated into the mixture. Scrape the bowl with the spatula to make sure all of the molasses has been added.
Store the brown sugar in an airtight container, like normal. Use however you'd like
Notes
For light brown sugar: Add 1 tbsp of molasses to 1 cup of sugarFor dark brown sugar: Add 2 tbsp of molasses per cup of sugarAlways store your brown sugar in an airtight container to minimize clumping.