Preheat the oven to 180°C (gas mark 4, 350°F) and grease a doughnut tray with melted butter.
Add an egg, milk, vanilla and melted butter into a large mixing bowl and mix until combined.
Pour flour, cocoa powder, salt, sugar, baking powder and bicarbonate of soda to the mixing bowl and mix together until a batter has formed.
Add crushed Oreos to the batter and mix until evenly distributed.
Spoon or pipe the Oreo donut mixture into the doughnut tray and bake for 8 to 10 minutes. Stick a skewer inside, if it comes out clean then it’s ready.
Once baked, leave the donuts to cool down for a few minutes before transferring to a cooling rack to cool down completely.
How To Make The Cream Cheese Icing
To make the cream cheese icing add icing sugar, cream cheese, vanilla extract and milk to the mixing bowl and mix together until combined. You can add more milk if necessary to change the consistency.
Once the donuts are baked and have cooled down completely.Dunk each donut into the cream cheese icing and place on a cooling rack icing side up. Then sprinkle with crushed Oreos and leave the icing to harden.