Take is bowl add maida,cornflour salt food red chilli powder, mix well add water & prepare thick batter

Cut cube shaped or as like you but not too big, put them in pan add water add salt boil 5 minutes check it them it they are soft or not.

Add potatoes in batter heat oil on high flame fry on high flame take out from oil, heat pan add oil add cumin seeds, ginger paste add onions cook for 2 minutes mix it well add soya sauce, chilli sauce,tomato ketchup,salt,Kasturi methi & add add in potatoes mix it well cook 2-3 minutes. Ready potato manchurian.