Preheat your oven to 350°F (175°C) and prepare a 12-cup muffin tin with cupcake liners.

In a sizable bowl, combine the flour, sugar, baking powder, baking soda, and salt, mixing them thoroughly.

In another bowl, cream together the softened butter and sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition, followed by the vanilla extract and buttermilk.

Gradually incorporate the dry mixture into the wet ingredients, stirring until just combined. Carefully fold in the crushed chocolate sandwich cookies.

Spoon the batter into the cupcake liners, filling each about two-thirds full. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool in the pan for 5 minutes before moving them to a wire rack to cool completely.

For the frosting, combine the powdered sugar, cocoa powder, milk, and vanilla extract in a bowl. Beat until smooth and creamy.

Once the cupcakes have cooled, pipe or spread the chocolate frosting on top of each one and place a mini chocolate sandwich cookie on each cupcake.