Preheat oven to 350 degrees F and place parchment paper on a baking sheet.

In the bowl of a stand mixer with paddle attachment, cream together butter and sugar. You can use a hand mixer as well. Mix in cocoa powder and milk.

In a medium bowl, whisk together flour, salt, baking powder, and baking soda.

Add dry ingredients slowly while mixing. Mix well.

Roll dough into small balls (about 1" wide) and place on prepared baking sheet.

Use your thumb to press down in the center of the balls.

Bake for 9 minutes until cookies look dry and start to crack a bit around the top. After removing from the oven gently press down the centers again with a small spoon. Allow to cool.

Melt the Ghirardelli's chocolate wafers as listed on the package. Fill the thumbprint centers with the chocolate. Crush the peppermints with the flat side of a kitchen mallet and sprinkle on top. Add some marshmallow bits.

Store in an airtight container.