Butter bottom and side of pan, then line bottom with a round of parchment.
Sift together flour, cocoa powder, baking soda, baking powder, and salt into a bowl.
Beat together butter and brown sugar in a large bowl with an electric mixer at medium-high speed until light and fluffy, 3 to 5 minutes.
Add eggs 1 at a time, beating well after each addition, then beat in vanilla.
Reduce speed to medium-low and add flour mixture and milk alternately in batches, beginning and ending with flour mixture (batter will appear curdled).
Transfer batter to cake pan and smooth top.
Bake until cake begins to pull away from side of pan and a wooden pick inserted into center comes out clean, 35 to 40 minutes.
Cool cake in pan 5 minutes, then invert onto a rack and cool completely, about 1 hour.
Chocolate Sauce
Crumble the cake with hands or food processor, and put crumbs into a large bowl.
Combine ½ cup chocolate, whipped cream cheese, and sugar in a medium bowl.
Mix this mixture into the cake crumbs thoroughly.
Form 1 tbsp-sized balls, and stick onto lollipop sticks.
Roll the cake balls in the melted chocolate.
Then dip in sprinklers and freeze for approximately 30 minutes to harden shell.