1. Allow the butter to go to room temperature so it is easier to work with (10 seconds in microwave of sit out of the fridge for 10-15 mins), place butter in a bowl and add both types of sugar. Cream together using a fork then add in the milk and vanilla, beat in to make a very thick paste.

2. Sift in the gluten free flour and baking powder and beat in using a wooden spoon, when it gets to stiff to use the spoon use your hands to work the dough around so it all combines together.

3. Add the chocolate chips to the bowl and use your hands to kneed the chips into the cookie dough.

4. Grease and line a square or rectangle tin (around 9" width, silicone or one with removable bottom will be best). Press the cookie dough into the tin.

5. Press the oreos into the top of the cookie dough then set aside.

6. To make the brownie, melt the dark chocolate and butter in a bowl, we just melted in the microwave for 1 and half mins checking and stirring every 20-30 seconds until smooth and silky.

7. In a separate bowl whisk the sugar and the eggs together until starting to get creamy, using a hand whisk is completely fine. Pour in the chocolatey mix and whisk again until thick and creamy.

8. Sift flour and cocoa powder into the chocolate and whisk once more until well combined. Pour on top of the oreos and make sure it is all well covered.

9. Place in an oven preheated to gas mark 4 and bake for an hour, at this point the brownie mix with still be at that quite sticky fudgy consistency, if you want it more spongy cook for another 10-15 mins.

10. Once cooked allow to go completely cold. This will take a good 8 hours or even overnight, don't cut until completely cold as it will collapse. (Handy tip if you are impatient, we allowed to cool for a few hours then placed in a freezer for 2 hours to cool down more rapidly).

11. Once cold, cut into 16 pieces and serve!