Preheat to 360 degrees F. Add cupcake papers to a cupcake pan.
In a stand mixer fitted with a paddle attachment, cream the butter, then mix in sugar.
Add in vanilla and sour cream. Mix until creamy.
Mix in egg whites slowly, then mix on medium until combined.
Alternate adding milk and flour. Add baking powder and mix until batter is fully combined.
Fold in ½ of the crushed candy cane. Do not overmix.
Using an ice cream scooper, fill papers with batter. Make sure to not overfill.
Sprinkle the other ½ crushed candy cane into papers. Swirl with a toothpick.
Bake for about 15-20 minutes.