Prepare chocolate chip cookies as directed in the original recipe, swapping out the chocolate chips for the 1 cup of M&M'sÂ®. Reserve 1/4 of the dough, and wrap the rest in plastic and place in the fridge for later use.
Preheat oven to 325 degrees. Grease a bundt pan with shortening or butter, then coat in an even layer of cocoa powder. Tap out the excess and set aside.
In a large mixing bowl beat the butter and sugar until light and fluffy, around 5 minutes. Beat in the eggs, one at time, until fully incorporated, then mix in the cocoa powder, vanilla extract, and sour cream.
Whisk together the flour, baking soda, and salt and slowly add to the mixture.
Gently beat in the boiling water on low speed.** Pour the batter into the prepared bundt pan.
Roll the cookie dough into small balls and plop them into the cake batter in the bundt cake, pressing down just slightly.
Bake for 60 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Allow the cake to cool for 10 minutes in the pan before flipping out onto a cooling rack to cool completely.
Remove the lid and foil from the icing, then place in the microwave and heat for 15 second intervals until smooth and pourable. Slowly pour over cooled bundt cake, allow to set, then cut up and serve!
* Omit the chocolate chips and use the M&M'sÂ® instead. Cover and refrigerate the remaining cookie dough for later use. ** Batter will be slightly runny, with a consistency more like mousse.