Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat.

1. In a large mixing bowl, beat together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
2. Add the egg and vanilla extract, and mix until fully incorporated.
3. In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking soda, and salt.
4. Gradually add the dry ingredients to the wet mixture, mixing until just combined. Add 2 tablespoons of milk if needed to adjust dough consistency. The dough should be thick but pliable.
5. Scoop about 1 ½ tablespoons of dough and roll it into a ball. Place the dough balls onto the prepared baking sheet, spacing them about 2 inches apart. Gently press each dough ball down slightly.
6. Bake for 8-10 minutes, or until the edges are set but the centers are still soft. The cookies will firm up as they cool, so don’t overbake them.
7. Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.
8. For the cream filling: Beat together the powdered sugar, softened butter, milk, vanilla extract, and salt in a medium bowl until smooth and creamy. Pipe the cream filling onto the cooled cookies using a piping bag or a plastic sandwich bag with the tip cut off.
9. For the glaze: In a small saucepan, melt the semisweet chocolate chips, butter, and milk over low heat, stirring constantly until smooth and fully combined. Drizzle the glaze over the cream-filled cookies.
10. Allow the glaze to set for a few minutes before serving. Enjoy your delicious Hostess Cupcake Cookies!