South indians make a variety of dishes (poriyal, paruppusili, vadai etc.) with these flowers.
The pictures are self explanatory, yet a small explanation.
Apply oil on your hands. Remove the bracts (red coloured petals).
Collect all the florets.
How to open the flowers?.. Gently rub the top edges of the flower on your palm. The flowers will open and you will find a hard stamen (KaLLan in Tamil) and husk(plastic like small petal). Remove the stamen and the plastic like petal.These are to be discarded and should not be used while cooking the flowers as they will be very hard.
Continue the procedure with all the blossoms.
Chop the blossoms finely and add to a bowl of diluted buttermilk to prevent discolouration. Vazhaipoo is ready to cook.