In a medium saucepan, melt chocolate chips and sweetened condensed milk over medium-low heat. Stir continuously until smooth and combined.
Remove from heat and stir in vanilla extract and cinnamon.
Sprinkle your desired amount of cinnamon sugar mixture over the top.
Let chill in the refrigerator 2 hours. Cut into 1-inch squares.
Notes
Storing and freezing: Store in an airtight container up to 2 weeks. It will last for another week or so if stored in the fridge. You may also freeze the fudge up to 2 months.