Preheat oven to 350°F (175°C) and prepare a 9×13-inch baking pan.
Mix dry ingredients (flour, cocoa powder, baking powder, baking soda, salt) in a medium bowl.
In another bowl, cream butter and sugar until fluffy; add eggs and vanilla extract.
Combine dry and wet ingredients alternately with buttermilk, then stir in hot water until smooth.
Pour batter into the prepared pan and bake for 25–30 minutes. Let cool completely.
Beat cream cheese until smooth, then whip in heavy cream, powdered sugar, and vanilla until light and fluffy.
Spread the cream mixture evenly over the cooled cake.
Tint shredded coconut pink using food coloring and a little milk if needed, then sprinkle evenly over the cream layer.
Chill for 1 hour before slicing into bars and serving.
