Directions

1. Preheat & prep — Preheat oven to 350°F (175°C). Line baking sheets with parchment paper. Whisk together flour, baking powder, baking soda, and salt in a bowl and set aside.

2. Cream butter & sugar — In a stand mixer or large bowl, beat softened butter and granulated sugar on medium-high until pale and fluffy (about 2–3 minutes).

3. Add egg, vanilla & sour cream — Beat in egg, vanilla, and sour cream until combined. Scrape down bowl.

4. Combine dry + wet — With mixer on low, add dry ingredients just until incorporated; do not overmix. The dough should be soft but hold shape. If too sticky, add 1 tbsp flour.

5. Chill dough — Scoop dough into 1.5–2 tbsp portions (or roll and cut). Chill on a tray 20–30 minutes — this keeps cookies from spreading too thin and yields a soft, cake-like texture.

6. Bake — Place cookies 2 inches apart and bake 8–10 minutes, until edges are set but centers are still pale. Remove from oven and let cool on sheet 5 minutes; transfer to wire rack to cool completely.

7. Make ultra-white buttercream — Beat butter 1–2 minutes until smooth. Gradually add powdered sugar, alternating with cream, on low then medium speed until smooth and pipeable. Add vanilla. Add Natural White Food Color a few drops at a time and beat until the frosting reaches a bright, neutral white—stop when satisfied. Taste and adjust texture with more cream or powdered sugar.

8. Frost & finish — Pipe or spread buttercream onto cooled cookies. Add sprinkles, sanding sugar, or leave smooth for a clean white cookie. Store in an airtight container between sheets of parchment at room temp up to 2 days (refrigerate up to 5 days; re-whip before using).