Grate bamboo shoot pieces and mince onion and garlic. Crush cumin seeds, Kalonji, Cinnamon and Cardamom and tie in a muslin cloth.
Place grated bamboo shoot, sugar, onion, garlic, chilli powder and salt with ¾ cup of water in a pan and cook over low heat with constant stirring until the sugar dissolves completely.
Drop the spice bag in the pan and simmer till thick syrup is formed. Remove the spice bag, add vinegar and cook for another few minutes.