Take condensed milk in a microwave bowl. Add cocoa powder and butter and mix.
Put in the microwave and cook on microwave HIGH for two to three minutes. Stir it and again cook for a minute.
Remove and add crushed biscuits and walnuts to it. And put it in the microwaave and cook further for two minutes.
Remove and pour it a greased thali and then keep the thali in the refrigerator till it sets. Remove and cut into pieces.