For Sponge:

1. Preheat the oven to 180C (OTG mode: upper rod + lower rod + fan). Grease two 6-inch round cake tins with oil and line them with butter paper. 
2. Sift together all-purpose flour, corn flour, baking powder, and baking soda in a bowl.
3. In another bowl, cream together melted butter and icing sugar.
4. Add vanilla essence to the creamed mixture and mix.
5. Add in the sifted dry ingredients and mix well.
6. Now add buttermilk in parts. Combine everything well and make a smooth batter.
7. Pour the batter into the prepared tins equally.
8. Bake in preheated oven at 180C (OTG mode: lower rod only) for 30-40 minutes or until a toothpick inserted in the centre comes out clean.

For Butterscotch Sauce:

1. Add all the ingredients in a heavy-bottom saucepan, i.e., brown sugar, salted butter, fresh cream, salt, and vanilla essence.
2. Bring the mixture to a boil and keep stirring. 
3. Let the sauce simmer until it starts to thicken.
4. Butterscotch sauce may take a few minutes to thicken, but to check for thickness, dip the back of a spoon in the sauce, and if it sticks to the spoon, it’s ready to be removed from heat.
5. Transfer it to a bowl and let it cool down.

For Frosting:

1. Add whipping cream and butterscotch sauce in a bowl, then beat them until a soft peak is achieved.

2. Transfer it to piping bags and keep it aside for further use.

For Assembly:

1. De-mould the cake from the tin with the help of a bent palette knife.
2. Divide the sponges into two parts using a cake leveller.
3. Now on the cake base, spread some frosting so that our cake doesn’t budge while layering or frosting.
4. Now place a sponge layer and soak it with soaking syrup using a pastry brush. 
5. Pipe frosting on top and smooth it out. Now spread some butterscotch sauce and sprinkle butterscotch nuts on top.
6. Place another layer of sponge and repeat the same process until we get four layers of sponges. Soak the top layer as well. 
7. For crumb coating, pipe thin layers of frosting all over the cake, smooth out using a palette knife and remove the excess with a scrapper.
8. Keep it in the freezer for about 15-20 minutes. 
9. After 15 minutes, remove the crumb-coated cake from the fridge and start piping frosting all over the cake for final coating.
10. Now spread butterscotch sauce on top and give a drip effect, using 1M nozzle pipe spirals on the top edge of the cake. 
11. Lastly, sprinkle crushed butterscotch nuts on top.