In a pan, roast chopped walnuts.Then in another pan, add in the chopped chocolate chunks, condensed milk, butter, cocoa powder and mix it all together until a smooth silky texture appears.Add in vanilla essence to the chocolate mixture and give it a final mix.Pour the chocolate fudge into a baking tray covered with butter paper and spread it out evenly.Sprinkle roasted chopped walnuts on top of it and let it cool in the refrigerator for 1 hour.Cut it into desired shapes and sizes. The chocolate fudge is ready to serve.