Preheat oven to 350 degrees and line pans with cupcake liners.
In a large bowl, combine cake mix, eggs, oil, milk, sour cream and vanilla extract and stir until smooth.
Fill cupcake liners 3/4 full and bake for 15-20 minutes or until and inserted knife comes out clean.
Frosting: Beat butter until smooth. Add peppermint and vanilla extract, cocoa powder and milk. Slowly add in 1 cup of powdered sugar at a time until you reach your desired consistency. If the frosting becomes too thick, add more milk.
Pipe onto cooled cupcakes and top with crushed candy canes!