In a mixing bowl, add 50g of butter, sugar, vanilla essence and oil and whisk is together
In another mixing bowl, add flour, cocoa powder, baking soda, baking powder and put it through a sieve
Now in the first mixing bowl, add the dry ingredients and sweetened condensed milk and milk as needed and make a batter
Grease the cake pan with butter and flour and add the batter and bake it for 35-40 mins. To check if its baked, put a toothpick into it, if its dry, its done if the batter comes with it, it needs more time to be done baking
While the cake's baking, take a mixing bowl over a boiler and add butter till its melted, then add marshmallow fluff and confectionery sugar to it
Take the bowl out of the boiler and whisk it in high speed till its light and fluffy
When the cake's done, decorate it with the icing made above as you please and you're good to go.