Best 15 min chocolate muffins ever

0. Preheat your oven on 180 degree C. 1. In a big bowl mix together flour, backing powder, salt, sugar and cocoa. 2.Make a hole in that mix and add a yolk mixed with milk and oil. Stir that well for few minutes until you get nice, smooth batter. 3. I personally always like to whisk egg white separately until it really nice and firm (with a pinch of salt for firmness) and than add in to the batter easily with spoon. 4. Then mix it really gently with spoon, or whisk, but mind to leave as much as possible air in dough. 5. Finally add 50 grams of grated dark chocolate or choco chips in that batter. 6. Prepare your muffin backing mold, grease it, fill with batter and then sprinkle every muffin with bit of a grated chocolate. 7. Bake for approximately 20-25 minutes.