Preheat your oven to 350°F (175°C).
Line your mini cupcake pan with cupcake liners.
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream together the unsalted butter and granulated sugar using an electric mixer on medium speed until light and fluffy.
Beat in the large egg and vanilla extract until fully combined, scraping down the sides as needed.
Gradually add the flour mixture to the butter mixture, alternating with the milk. Start and end with the flour mixture, mixing just until combined without overmixing.
Using a small cookie scoop or spoon, fill each mini cupcake liner about two-thirds full with batter.
Bake for 10-12 minutes, or until a toothpick inserted into the center comes out clean.
Remove cupcakes from oven and let cool in the pan for 5 minutes, then transfer to a cooling rack to cool completely.