Directions

1. Preheat the oven to 350°F. Lightly grease two 15x10 inch baking pans and line with parchment paper.
2. Mix the cake mix, 1 1/4 cups milk, vegetable oil, eggs and vanilla extract in a large bowl on medium speed for 2 minutes. Divide the batter evenly between the two pans.
3. Bake for 12-15 minutes or until a toothpick inserted into the center of each cake comes out clean. Allow to cool for 5 minutes.
4. Lightly dust two clean sheets of parchment paper with powdered sugar. Flip the cakes onto the parchment paper and remove the baked parchment paper. Beginning with the short end of the cakes, roll each cake with the parchment paper into a log and allow to cool completely.
5. Beat the butter in a larger mixer bowl on medium speed for 3-4 minutes. Add the powdered sugar and beat on medium-low speed until incorporated. Add the peppermint extract and enough of the remaining milk until the desired consistency is achieved. Beat the buttercream on medium-high speed for 4-5 minutes.
6. Unroll the cakes. Divide the peppermint buttercream evenly between the cakes and spread, allowing for a 1/2-inch border around the cakes. Reroll the cakes, without the parchment paper, tightly around the buttercream. Wrap in plastic wrap and refrigerate for at least 1 hour.
7. Remove the plastic wrap, slice off the ends and arrange the cakes on a serving platter. Lightly dust with powdered sugar.