Preheat your oven to 325 degrees Fahrenheit (165 degrees Celsius).
In a large bowl, cream the softened 84% butter with sugar until light and creamy.
Add mayonnaise and vanilla extract, then mix until well incorporated.
Incorporate the egg and mix until fully integrated.
In another bowl, sift the flour with baking powder.
Gradually add the flour mixture to the butter mixture, stirring well after each addition, until the dough is homogeneous.
Shape the dough into spirals on an ungreased baking sheet, spacing them slightly apart.
Bake the prepared cookies in the preheated oven for 14 to 18 minutes, or until lightly golden around the edges.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Once cooled, enjoy these delicious butter cookies with a glass of milk or a cup of coffee. Bon appétit!
