Preheat your oven to 180°C (350°F). Line the baking sheet with baking paper and put aside.
Sieve together the flour, baking powder, and salt. Put aside.
Place the butter and chocolate in a metal heat-proof bowl over a pot with simmering water. Let it melt until smooth stirring occasionally. Remove from the heat and add the cocoa powder, whisk until combined.
In a large bowl, whisk together the eggs, granulated and brown sugars, oil and vanilla extract.
Add the warm chocolate mixture and whisk until smooth.
Gradually, two tablespoons at a time, add the flour to the batter, and mix with a spatula after each addition.
Chill the dough in the fridge for 20 min, it will make it easier to handle.
Put the icing sugar in the small bowl, no need to sieve it, unless it's very lumpy. Break your milk chocolate into cubes and prepare some unsweetened cocoa powder to sprinkle on top. Using a cookie scoop (!), take a portion of the dough and drop it into the icing sugar, make sure it's coated all around. Touch the dough only when it's fully covered with the icing sugar, only then it's easy to be shaped into the balls and can be placed on top of the baking sheet. Place a cube of milk chocolate on top of each cookie and give it a final sprinkle of the unsweetened cocoa powder.
Bake for 8-9 min, and let the cookies cool down on the wire rack.
