In a large mixing bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes. Add in the large egg and vanilla extract, beating until well combined and smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add the dry ingredients into the wet mixture, mixing on low speed until a soft dough forms, about 1-2 minutes.

Using a spatula, gently fold in the mini chocolate chips or any desired mix-ins until evenly distributed throughout the dough.

Divide the dough into two equal halves and roll each half into a log, approximately 2 inches in diameter. Wrap each log tightly in plastic wrap and refrigerate for at least 2 hours.

Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

Unwrap the chilled dough logs and slice them into ¼-inch thick rounds. Arrange them on the prepared baking sheets.

Bake the cookies for 10-12 minutes, or until the edges are lightly golden and the centers look set.

Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to wire racks.