Preheat oven to 350º F. Grease 9 x 13 inch cake pan and dust with flour.
Mix the cocoa with boiling water in small bowl, stir until smooth. Set aside to cool.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
Using an electric mixer, beat the butter and granulated sugar until fluffy.
Add the eggs, one at a time, beating well after each one.
Stir in the vanilla extract.
Gradually add the cocoa mixture.
Blend in the flour mixture, alternating with the milk and sour cream. Mix until combined. (do not over-mix)
Pour the batter into the prepared pan.
Bake for 30-40 minutes, wooden toothpick inserted in center comes out clean.
Cool completely. This recipe will make approximately 50 Cake Pops.