Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a separate bowl, cream the butter and sugar until light and fluffy, about 2-3 minutes. Add the egg and vanilla extract, mixing until well combined.

Gradually add the dry ingredients to the wet ingredients, alternating with the milk. Begin and end with the flour mixture, mixing just until combined.

Scoop tablespoonfuls of dough onto the prepared baking sheet, spacing them about 2 inches apart. Flatten each ball slightly to create a uniform surface.

Bake for 10-12 minutes or until the edges turn golden. Remove from the oven and allow them to cool completely on a wire rack.

In a medium bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Pipe or spoon some of the cream filling onto the bottom of half of the cooled cookies.

Top with the remaining cookies to form sandwich cookies.

In a small saucepan, heat the heavy cream for the ganache until it just starts to simmer. Remove from heat.

Add the melted chocolate chips to the cream and stir until the mixture is smooth and glossy.

Dip the sandwich cookies into the ganache, letting the excess chocolate drip off. Place the cookies on a wire rack to set.