Slice the cake horizontally into three slices. Mix custard powder in a little cold milk. Heat the remaining milk in a pan, add the custard powder mixture and cook, stirring continuously, till it begins to thicken.
Add sugar and stir till it dissolves. Set aside to cool. Heat a cup of water in a pan. Add one teaspoon instant coffee powder and mix. Set aside to cool.
Add hung curd to the cooled custard and mix. Add the whipped cream and mix well. Place the base slice of the cake in a glass bowl. Pour some of the coffee decoction over it and let it soak well.
Spread some of the custard mixture all over it. Soak the remaining cake slices in the remaining coffee decoction.
Place another cake slice over the one in the bowl and spread some of the custard mixture all over it. Cover it with the third cake slice.
Pour the remaining custard mixture over it and spread it over the top and the sides of the sandwiched cake. Put the remaining instant coffee powder in a small sieve and sprinkle it all over the top of the tiramisu.
Keep it in the refrigerator to set for at least one and a half hours. Serve chilled.