Make the Cookie Dough:

1. In a bowl, whisk together flour, baking powder, and salt. Set aside.
2. In a large bowl, beat butter and sugar until light and fluffy (about 2 minutes).
3. Mix in egg, vanilla extract, and peppermint extract until combined.
4. Gradually add the dry ingredients, mixing just until a soft dough forms.
5. Divide the dough in half. Tint one half with red food coloring to create a vibrant red dough.
6. Wrap both doughs in plastic wrap and refrigerate for 30 minutes.

Create the Striped Pattern:

7. Roll out both doughs separately on a floured surface to about ¼-inch thickness.
8. Cut each dough into ½-inch wide strips and alternate red and white strips side by side.
9. Lightly roll over the dough to seal the strips together.
10. Use a round cookie cutter to cut out cookies and place them on a parchment-lined baking sheet.

Bake the Cookies:

11. Preheat oven to 350°F (175°C).
12. Bake for 8–10 minutes, or until the edges are lightly golden.
13. Let cookies cool completely before assembling.

Make the Peppermint Filling:

14. In a bowl, beat butter until creamy. Gradually mix in powdered sugar and peppermint extract.
15. Add heavy cream as needed until smooth and spreadable.

Assemble the Sandwich Cookies:

16. Spread or pipe peppermint filling onto the bottom of half the cookies.
17. Top with the remaining cookies and gently press together.
18. Roll the edges in crushed peppermint candies for extra decoration.