You will start off preparing the kappa - first chop off the ends, slice it into thick rounds, then peel using a paring knife. Then slice the thick rounds lengthwise into long slices about an inch thick. Then chop them roughly into bite-sized pieces.
In a medium-sized sauce pan, add 3 quarts (about 2 liters) water, kappa pieces, salt, and bring to a boil. Simmer for 15-20 minutes or till tender.
While the kappa is cooking, using a blender, gently crush the coconut, garlic, and Serrano pepper.
Once the Kappa pieces are cooked, in a small skillet or kadhai, heat oil and splutter the mustard seeds. Add curry leaves and red chilli flakes. Drain the kappa pieces and add them to the seasoned oil and mix well.
Mix the crushed coconut mixture with the kappa pieces and stir well.
Serve hot.