Preheat oven to 350F.  Line muffin tins with paper liners.

In a large mixing bowl, whisk flour, cocoa powder, sugar, baking soda, baking powder, and salt. Make a well in the center of the dry ingredients and add milk, oil, vanilla, and eggs.  Stir until just combined, scraping bottom of bowl with a rubber spatula to incorporate all of the flour.

Fill cupcake liners with 1/4 cup of the batter (no more than two thirds full).  Bake 18 to 22 minutes or until a toothpick comes out clean.  Transfer to a cooling rack and cool completely.

Prepare the cookie dough in a large mixing bowl.  Beat butter and sugars with mixer on medium speed until light and fluffy.  Beat in milk and vanilla.  Add flour and salt until all incorporated.  Set aside 1 cup of the dough for the frosting, stir in 1/3 cup of the chocolate chips.

To prepare the buttercream, cream the butter until fluffy, 1 to 2 minutes.  Slowly add powdered sugar, 1/2 cup at a time, beat until smooth.  Add the reserved plain cookie dough and mix on medium high until light and fluffy about 2 to 3 minutes.

Using a small knife, cut a cone shaped piece of cake from the top of each cupcake.  Pinch off the tips and discard or eat. Fill with the cookie dough and replace the tops. Spread or pipe on frosting, being sure to cover the seams.  Sprinkle with remaining 1/3 cup chocolate chips.

Note: when I made these I only used half the frosting and it was plenty.