To make the chocolate cookies preheat the oven to 350 degrees.

In a large bowl combine the flour, cocoa powder, baking soda, and salt. Mix well to combine.

In another large bowl cream together the butter and sugar. Add in the eggs and mix well.

Stir in the vanilla and coffee and mix well.

Add half the flour mixture to the butter mixture and mix well to combine.

Slowly add the chocolate milk, stirring frequently, until well combined.

Add the remaining flour mixture and mix until just combined.

Using a 4 Tablespoon cookie scoop, scoop the chocolate dough onto a cookie sheet leaving 3 inches between each scoop.

Bake for 10-12 minutes or until the cookie cakes spring back when touched. All to cool on the baking sheet for 5 minutes before removing to a wire rack to cool completely.

To make the buttercream frosting place the butter in a large bowl and use a mixer on medium speed to beat until smooth. Add the powdered sugar a cup at a time, mixing on medium speed after each addition.

Add the milk and vanilla and mix on medium speed for 1 minute. Increase to high speed and beat an additional minute.

Divide the frosting into 6 bowls. Dye each one a different color: red, orange, yellow, green, blue, and purple.

Turn 12 cookies flat side up. Pipe or spoon a different colored frosting all over two cookie,s top with another cookie so that you have 12 whoopie pies with 6 different colors of frosting.