Preheat oven to 350ºF and butter a 9 x 13 sheet cake pan. Place parchment paper large enough to have overhang on both sides and press down to coat. Flip the paper and press down to coat; set aside.
In a bowl, add flour, baking powder and salt; whisk to combine and set aside.
In the bowl of a stand mixer, add sugar and butter. Using the paddle attachment, process on medium-high speed until blended.
Add eggs, one at a time, mixing well between each addition and cleaning the sides and the bottom of the bowl as needed.
Add orange zest and vanilla; process until blended, about 45 seconds.
Add half dry ingredients and half milk; process on low speed until just combined. Add the remaining dry ingredients, milk and orange juice; mix until just combined, cleaning the sides and the bottom of the bowl as needed.
Pour the batter into the prepared cake pan and level it out using a spatula.
Transfer to the preheated oven and bake for 25 minutes or until a cake tester inserted in the center comes out clean.
Remove from the heat and let it cool for 10 minutes before lifting the cake from the pan to a wire rack. Place another wire rack on top and quickly invert it. Gently peel off the parchment paper and discard it.
Place wire rack again and reinvert the cake. Let it cool completely on a wire rack for 30 minutes before slicing into 1 ½ to 2-inch squares.
Place the squares into a container and transfer to the fridge for at least 3 hours.
In a bain-marie over medium-low heat, add butter pieces and melt it.
Add sifted cocoa powder and confectioners’ sugar; add milk. Stir until the mixture is smooth without lumps. Stir in vanilla extract and remove from the heat.
Working with one square at a time, dip it in the chocolate. Using a couple forks, flip and toss it around until entirely coated.
Let excess chocolate frosting drip off before transferring onto a wire rack sitting over a baking sheet
After a few are done, coat them in shredded coconut flakes making sure they’re nicely covered. Place them back on the rack to dry while doing the others.