Preheat the oven to 350 degrees F. Line a 15X10X1 baking sheet with parchment paper and spray the paper with a non-stick spray.
In a large bowl, combine the cocoa powder, flour, baking powder and salt.
In a separate bowl, whisk together the eggs and sugar. Then add in the butter and vanilla. Whisk until just combined.
Then stir (by hand) in the dry ingredients (flour mixture) into the wet ingredients (egg mixture). Stir until just combined and be careful not to over mix.
Then using a spatula spread the batter into the baking sheet. Bake for 11-13 minutes or until the center of the cake springs back when touch.
Lay out a clean kitchen towel on the counter and sprinkle well with powdered sugar. Place cooked cake on top of prepared towel. Starting on the small end, roll up the cake inside the towel. You do this just to get the cake to cool in the final shape. Let cool completely on a wire rack, about 1 hour.
Make filling. Use an electric mixer (hand held or stand up), whip the heavy cream and powdered sugar until stiff peaks began to form (about 3-5 minutes).
Unroll cake. Spread the whipped cream all over the top side of the cake.
Roll the cake back up. Set aside while you prepare the chocolate ganache topping.
In a microwave safe bowl, heat the chocolate chips and heavy whipping cream in 30 second intervals until the chocolate is completely melted. Stir between each interval.
Then stir in the powdered sugar and gradually stir in the milk until the ganache is a pouring consistency.
Pour the chocolate ganache evenly over the top of the cake. Refrigerate for 20-30 minutes to let the chocolate set.
Then slice, serve and enjoy!
Notes
Store the leftover cake in the refrigerate for up to 3 days.