Chocolate Burfi

Butter - 50 grams   
Milkmaid/Condensed milk  - 1 tin/400 g  
Sugar - 1/2 cup   
Cocoa powder - 1/2 cup   
Chopped nuts - 1/2 cup  
Chopped pista - for garnish
  Grease a tray with butter and keep aside.
  Mix together butter, milkmaid, sugar, cocoa powder and chopped nuts in a thick bottomed pan. Keep stirring the mixture continuously on low flame, till the mixture leaves the sides of the pan.
  Pour the mixture into the greased tray and spread it evenly. Sprinkle the chopped pista over the surface of the mixture.
  Set aside and allow the mixture to cool. Refrigerate for about 10 to 15 minutes. Then cut out into desired shapes.