In a large mixing bowl, cream together the softened butter, granulated sugar, egg, and vanilla extract until smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until the dough is fully combined.

If desired, fold in any optional add-ins such as sprinkles, nuts, or chocolate.

Divide the dough in half and shape each portion into a log approximately 1 1/2 to 2 inches in diameter.

Wrap the dough logs in plastic wrap and refrigerate for a minimum of 4 hours, up to overnight, to firm up.

When ready to bake, preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

Slice the chilled dough into 1/4 inch thick rounds and place them on the prepared baking sheet, spaced about 2 inches apart.

Bake in the preheated oven for 10 to 12 minutes, or until the edges are just turning golden brown.

Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.