Preheat your oven to 180C/160C Fan and line two 8"/20cm tins with parchment paper!
Chop your Oreos into quarters or slighlty smaller - but still so there are chunks.
Beat your butter and sugar together until light and fluffy. I use my stand mixer with the beater attachment!
Add in your eggs, flour and vanilla and beat again till smooth!
Finally, add in your oreos and just lightly fold through!
Split the mixture between the two tins evenly, and then bake in the oven for about 28-35 minutes! I test my cakes with a skewer, but also for the sound of bubbling/crackling - if they still make the noise they need a bit longer baking!
Let the cakes cool in the tins for 10 minutes, and then on a wire rack.
For the Buttercream
Make sure your butter is at room temperature - I don't recommend using a spread for the buttercream, I use foiled block butter.
Beat the butter on it's own for a few minutes to loosen it and make it lighter!
Add in the icing sugar, and beat again for a few minutes - I use my stand mixer with the beater attachment again!
Once it's smooth, add in your oreo crumbs - for this you want the oreos to be a fine crumb! I don't take the creme out of the Oreos.
For the Decoration
Get your first cake onto your plate/board - spread half the buttercream on top!
Add your second cake, and the second half of buttercream.
Decorate with some chopped oreos and some more crumbs! Enjoy!
Notes
If you want to make a three-layer cake for this to make it more 'showy' and better for a birthday - you will want to use 400g of butter, sugar and flour, with 8 medium eggs - then use 250g of chopped Oreos in the sponges. Split that between three 8" tins, and bake for 30-35 minutes. Use 1.5x the buttercream!!
This cake will last for 3-4 days once baked!
If you want to use large eggs, use four large eggs and use 240g of butter/sugar/flour!
You can use any flavour oreo you like - or even the double stuffed! I just used the original!