In a heavy bottom non-stick pot, add the crumbled khoya and jaggery powder and cook on a medium flame until all the jaggery has melted completely and well blended with the khoya mixture. This may take around 5-6 minutes.
Add unsweetened cocoa powder and mix well.
Cook the mixture for another minute or so and put off the flame. Do not cook for longer, as it may turn hard and chewy and can be difficult to shape.
Remove the mixture on a plate to cool down enough to handle.
Make six equal balls from the mixture and shape them as diyas. If you are having trouble shaping the diya, it's okay. Just flatten the ball slightly , top with some chopped pistachio and enjoy as chocolate khoya peda.