Preheat the oven to gas mark 200C
Sift the flour, cocoa powder, baking powder and salt into a large bowl.
In a separate bowl mix together the egg, sugar, milk and melted butter.
Return the dry ingredients to the sieve and sift them straight on to the egg mixture (this double sifting is essential because there won’t be much mixing going on).
Take a large spoon and fold the dry ingredients into the wet ones - quickly, in about 15 seconds.
Don't be tempted to beat or stir, and dent be alarmed by the rather unattractive, uneven appearance of the mixture: this is what will ensure that the muffins stay light.
Now fold the chocolate drops into the mixture - again with a minimum of stirring, just a quick folding in.
Divide the mixture between the muffin cups about 1 heaped teaspoon in each, and bake on a high shelf in the preheated oven for 10 minutes, until well risen.
Then remove the muffins from the oven and cool in the tins for 5 minutes before transferring them to a cooling tray.