Preheat oven to 350F. Lightly grease and flour a bundt pan.
In a large bowl of a standup mixer with a paddle attachment add cake mix, eggs, water, sour cream and oil; blend on low speed for 30 seconds, until moistened, scraping down the bowl. Turn up to medium speed and mix for 2 minutes. Remove one cup of batter and set aside.
Pour the remaining batter into the prepared bundt pan. Take the reserved one cup of batter and add the red food coloring and peppermint extract. Stir well to combine. Drop by spoonfuls over top of the batter in the bundt pan and with a knife swirl.
Bake for 45-50 min. until cake springs back or cake tester comes out clean. Cool 10 min. in pan and then turn onto a serving plate.
In a medium saucepan mix together the milk, chocolate and sugar over medium heat stirring constantly until it begins to boil. Remove from heat and add butter and peppermint extract.
Decorate the cake as you would like to. I just piped on little red dots with tube icing for ornaments and sprinkled it with icing sugar.
Serve the cake with the warm Chocolate Mint Sauce.