For Cake Batter:

1. Preheat the oven at 180C (OTG mode : upper rod + lower rod + fan). Grease and line two 6-inch round tins.
2. In a bowl, mix milk and apple cider vinegar. Keep aside.
3. In a new bowl, cream butter and sugar until light and fluffy. Now add curd and vanilla essence and mix.
4. In another bowl, sift together flour, baking powder, baking soda, and salt.
5. Now add dry ingredients and milk alternatively into the creamed butter mix (start and end with dry ingredients) and form a smooth batter. 
6. Lastly, fold in crushed Oreos.
7. Now divide the batter equally between the tins and bake at 180C (OTG mode: lower rod only) for 20-25 minutes or until a toothpick inserted at the center comes out clean.

For Buttercream:

1. In a bowl, beat unsalted butter until it turns pale and fluffy.
2. In a new bowl, mix milk and icing sugar until sugar dissolves. 
3. Add milk and icing sugar mixture to the creamed butter gradually while beating.
4. Grind oreos in a mixer and then add them to the buttercream. Give everything a quick mix.

For the soaking syrup:

1. In a bowl, mix water and vanilla essence. Keep aside for further use.

For Ganache:

1. Melt dark coverture and warm the cream. 
2. Mix the two until a smooth ganache forms. 

Assembly

1. Cut each sponge into two equal layers using a metal cake leveler. You will have four sponge layers. 
2. Prepare a simple soaking syrup by mixing 100ml of water with 1 tsp vanilla essence. 
3. Place the cake board on a turn table and put buttercream in the center. 
4. Place the first sponge layer on the board. Now soak it well with soaking syrup. 
5. Pipe the oreo buttercream on the sponge and spread evenly using a palette knife. Now add some crushed Oreos.  Place the second sponge layer and repeat the same above steps for layering.
6. Place the cake in the freezer for 15-20 minutes. 
7. Now, take out the cake and frost the cake with a final coat of buttercream. Use a palette knife and metal Scraper for a smooth finish. Freeze the cake again for 15-20 minutes. 
8. Transfer leftover buttercream to a piping bag fitted with a 1M nozzle. Spread the ganache on top and the sides for a drip effect. Decorate the top edge by piping ruffled blobs. 
9. Place chocolate balls and chocolate vermicelli on the blobs to complete the look.