Preheat your oven to 350°F and line 2 baking sheets with parchment paper.

In a large bowl, whisk together flour, baking powder, baking soda, and kosher salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat shortening and sugars, on medium speed until fluffy, scraping down the sides as necessary.

Reduce the mixer speed to medium-low and add the eggs, one at a time, mixing just until combined. Scrape down the sides of the bowl as needed.

Slowly pour in the buttermilk mixture while mixing on low speed. Gradually add the flour mixture in three additions, mixing until just combined. Scrape down the sides of the bowl and mix for a few seconds longer until only a few streaks of flour remain.

Drop 2 tablespoonfuls of dough onto the prepared baking sheets, spacing them 2 inches apart. Bake for 9 to 11 minutes, just until the edges are golden brown. Cool on the baking sheet for 10 minutes before transferring to a wire rack to cool completely. Repeat with the remaining dough.

In a small saucepan over low heat, melt butter. Add brown sugar, stirring constantly until smooth. Stir salt and milk. Remove from heat and gradually add confectioners sugar, 2 tablespoons at a time, until a spreadable consistency is achieved. Let the glaze sit to cool until thickened.

Once the cookies are completely cooled, drizzle the glaze over the top of each cookie. Allow the glaze to set before serving.