Line an 8-inch x 8-inch baking pan with foil or parchment paper, leaving some hanging over the edge. Set aside.
Mix the cinnamon and sugar in a small bowl until thoroughly combined. Set aside.
Add the chocolate chips and butter to a medium saucepan over medium-low heat. Cook until melted and smooth. Remove from the heat.
Add the container of frosting to the saucepan and place back over low heat. Stir constantly until the fudge mixture is smooth and the frosting is melted.
Pour the fudge mixture into the prepared pan and spread into an even layer. Sprinkle all over the cinnamon sugar over the fudge.
Let the fudge sit on the counter for at least 2 hours to set up.
Once set, use the parchment paper to lift the fudge from the pan. Peel off the paper and cut the fudge into 25 pieces (5x5 grid).
Notes
Recipe yield and nutritional information will vary depending on how big you cut the fudge squares.