Mix the dry ingredients.
Combine the powdered sugar, desiccated coconut, and milk powder in a large bowl. Stir thoroughly, breaking up any lumps.
Add the condensed milk.
Pour in the sweetened condensed milk. Mix with a sturdy spatula, then use clean hands to work the mixture together like dough until evenly combined.
Chill the filling.
Cover and refrigerate for 30 minutes, until firmer and easier to shape.
Shape the bars.
Weigh out 20–22 g of filling per bar. Press each portion firmly together and shape into a small rectangle with rounded ends. Compress all sides so the filling does not crumble. Place on a parchment-lined tray.
Melt the chocolate.
Place the chopped chocolate in a dry, heatproof bowl over gently simmering water, without letting the bowl touch the water. Stir until smooth, then remove from the heat. Keep water and steam out of the chocolate.
Coat the bars.
Dip each coconut bar into the melted chocolate using a fork. Coat all sides, lift out, and let excess chocolate drip back into the bowl. Place on a wire rack set over parchment paper.
Make the ripples.
As the coating begins to thicken but is still soft, gently mark the top with the tip of a small knife. Avoid pressing through to the filling.
Let set.
Allow the chocolate to harden completely before carefully removing the bars from the rack. Refrigerate briefly if needed to help the coating set.