In a mixer, stir together the butter, sugar, flour, cocoa powder, and baking powder.
Whisk together the egg and milk and slowly drizzle into dry ingredients. Do not overmix.
In the meantime, melt the dark baking chocolate. Stir and let cool. Drizzle and fold into cake batter.
Scoop into lined muffin tins and bake until done - springy to the touch. Let cool before frosting.
To make frosting, whisk butter and sugar until creamy. Drizzle in coconut milk slowly. Follow by adding melted COOLED white chocolate. Whisk until fluffy. Decorate cupcakes and top with coconut flakes.
Notes
These were also filled with passion fruit curd made in Hawaii by Paradise Sweets. I find that using an apple corer to scoop out the center of the cupcakes works well.