In an idli maker pour some salt onto the base of it, cover and put it over gas to preheat.
Break the biscuits into small pieces and put them into electric grinder or mixer.
Grind the biscuits into fine powder and put it into a mixing bowl.
Add milk into the mixing bowl and mix.
Add a packet of eno or fruit salt into this, mix well and immediately transfer the contents into a baking dish.
Put the baking dish onto the gas oven over salt by putting the stand over it. And cover it with the lid.
Bake for around 10 to 20 minutes depends on the size of the cake. Check in between by inserting a toothpick in the cake whether it is done or not. If the toothpick comes out clean then your cake is ready.
Serve the cake as it is, as this biscuit cake is full of flavors and requires nothing to complete it. If you wish then you can also serve this along with melted chocolate or by doing some icing if making for a occasion.