1. Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

2. Whisk together flour, baking powder, baking soda, and salt in a medium bowl.

3. Cream butter and sugar in a large bowl for 2–3 minutes until light and fluffy.

4. Beat in egg, sourdough discard, peppermint extract, and vanilla extract until smooth.

5. Gradually fold dry ingredients into wet mixture until just combined.

6. Stir in crushed peppermint candies and white chocolate chips if using.

7. Cover and refrigerate dough for 30–45 minutes.

8. Scoop 1½-tablespoon portions of dough and roll into balls.

9. Optionally dip tops of dough balls in coarse sugar or crushed candy before baking.

10. Place dough balls 2 inches apart on prepared baking sheets.

11. Bake for 10–12 minutes until edges are lightly golden and centers remain soft.

12. Let cookies rest on baking sheets for 5 minutes, then transfer to a wire rack to cool completely.

13. Decorate cooled cookies with melted white chocolate drizzle and extra crushed peppermint if desired.