Cocoa is known to be good for heart. 1-2 ounces of dark chocolate, taken few times a week, is recommended by Real Age.
One ounce is 28.34 grams. Dark Chocolate typically has has 70% cocoa. Bournville was recently launched in India. It has 44% of fine cocoa from Ghana. It comes at a retail price Rs. 75 for 80 to 90 grams. I prefer to eat Cocoa powder(primarily to avoid sugar). I use Cadbury's 200g cocoa powder for Rs. 90.

p.s. - Real Age article also cautions that Cocoa is the highest contaminated food item with Lead. I need not explain what harm lead can cause. Head against Heart.