1. Preheat oven to 225°F (110°C) and line two baking sheets with parchment paper.

2. Ensure your mixing bowl and beaters are completely clean and grease-free.

3. In the bowl, beat egg whites on medium speed until foamy.

4. Add cream of tartar and salt, then continue to beat until soft peaks form.

5. Gradually add sugar, one tablespoon at a time, beating until stiff, glossy peaks form.

6. Sift in cocoa powder and add vanilla extract. Gently fold into the meringue without deflating.

7. Transfer the meringue into a piping bag fitted with a star tip.

8. Pipe small rosettes onto the baking sheets, leaving a bit of space between each.

9. Bake for 1 hour and 15 minutes, then turn off the oven and leave cookies inside for another hour.

10. Once fully cooled, store in an airtight container at room temperature for up to 7 days.