Grease a pan with melted butter/ghee and keep aside
In a mixing bowl mash Banana with potato masher/mathu. If there are small lumps it goes away while cooking. Add sugar, salt and mix well
Transfer it into a heavy bottomed pan and cook on medium heat
Add raisins and corn flour and continue cooking, stirring occasionally. Cook still it starts selparating from the pan with glossy texture. Add ghee and cook for a minute till it begins pulling away from the sides
Transfer the halwa to the greased pan and level the top. Chill it for an hour and cut them