Preheat your oven to 350°F (175°C). Line your baking sheet with parchment paper to prevent sticking and make cleanup easier.
In a large mixing bowl, beat the chilled salted butter and brown sugar together using an electric mixer or whisk until light and fluffy, about 2-3 minutes.
Add the medium egg and vanilla extract to the butter-sugar mixture. Mix until fully combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt to evenly distribute the dry ingredients.
Gradually add the dry ingredients to the wet mixture, stirring until just combined to form a soft dough.
Use a tablespoon or cookie scoop to portion the dough and roll into small balls. Place them spaced apart on the prepared baking sheet.
Bake in the preheated oven for 10-12 minutes, or until edges are lightly golden. Centers may look slightly underbaked but will firm as they cool.
Let the cookies cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely. Enjoy with tea or coffee!