1. Preheat the oven to 350°F and line a 12-cup muffin pan with cupcake liners.

2. In a medium bowl, whisk together the flour, baking powder, and salt.

3. In a large mixing bowl, beat the butter and sugar until light and fluffy.

4. Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.

5. Stir in the melted white chocolate and sour cream until smooth.

6. Add the dry ingredients in two additions, alternating with the milk, and mix just until combined.

7. Divide the batter evenly among the cupcake liners, filling each about two-thirds full.

8. Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out clean.

9. Cool the cupcakes in the pan for 5 minutes, then transfer them to a wire rack to cool completely.

10. For the frosting, beat the butter until creamy, then gradually add the powdered sugar.

11. Mix in the heavy cream, vanilla extract, and peppermint extract until the frosting is fluffy and smooth.

12. Pipe or spread the frosting over the cooled cupcakes, then top with crushed candy canes and mini candy canes if desired.