1. Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.

2. In a bowl whisk flour, baking powder, baking soda, and salt.

3. In a mixing bowl beat butter and granulated sugar until light and creamy.

4. Add eggs one at a time, then stir in sourdough starter, milk, peppermint extract, and vanilla.

5. Fold dry ingredients into the wet batter until just combined, then stir in crushed candy canes or chips.

6. Divide batter among 12 liners and bake for 18–22 minutes until a toothpick comes out clean.

7. Let cupcakes rest in the pan 5 minutes, then transfer to a cooling rack to cool completely.

8. Melt white chocolate over a double boiler and let cool to 90°F (32°C).

9. Beat softened butter until pale and fluffy, then slowly add cooled white chocolate.

10. Gradually add powdered sugar and cream, beating until smooth and pipeable. Add salt and optional peppermint extract.

11. If frosting is too soft chill for 10 minutes then rewhip.

12. Pipe frosting onto cooled cupcakes in spirals or swoosh with an offset spatula.

13. Garnish with crushed candy canes, edible glitter, or chocolate curls.

14. Store frosted cupcakes in a cool place or refrigerate; bring to room temperature before serving.