Preheat oven to 350. Grease 3 (9-inch) round cake pans, dust with flour, and line bottom with parchment or wax paper.
Sift together flour, cocoa powder, baking powder, and salt.
Blend milk, oil, and vanilla extract in a separate bowl.
In a large mixing bowl with electric mixer on medium speed, cream butter with sugar until light and fluffy. Add eggs one at a time, beating well after each addition.
Add flour mixture to butter mixture alternately with milk mixture, beating after each addition just until smooth. Divide batter evenly into prepared pans.
Bake 25 minutes or just until a knife or toothpick inserted in the center of layers comes out clean. Remove from oven, cool 10 minutes on a wire rack. Remove from pans and allow layers to cool completely before icing.
Combine chocolate chips and condensed milk in saucepan over gentle heat and stir continuously until chocolate has melted completely. Remove from heat and stir in sour cream. Add coconut, stir until combined, and allow icing to cool slightly. Frost between layers, and top and sides of cake before icing has completely cooled.