1. Cream butter and sugar in a stand mixer for 3–4 minutes until light and fluffy.

2. Add egg and vanilla, then mix well, scraping down the bowl as needed.

3. In a separate bowl, whisk together flour, salt, and baking soda.

4. Gradually add dry ingredients to butter mixture on low speed until combined.

5. Divide dough into three equal parts. Color one red, one green, and leave one plain.

6. Shape each dough into a ball, wrap in plastic, and chill for 1 hour.

7. Roll each dough between parchment into 7-inch squares; chill again for 15 minutes.

8. Stack red, green, then plain dough layers, and roll into a 12×8-inch rectangle.

9. Remove top parchment and tightly roll dough lengthwise into a log. Wrap and freeze for 1 hour.

10. Preheat oven to 350°F and line baking sheets with parchment paper.

11. Slice dough log into 1/3-inch cookies. Roll edges in red sanding sugar.

12. Place cookies 1 inch apart on baking sheets and bake 8–10 minutes until set.

13. Cool for 1 minute on sheet, then transfer to a wire rack to cool completely.

14. Store cooled cookies in an airtight container.