Wash and peel the pearl onions.
Slice the pearl onions in half, keep aside.
Wash the tapioca tubers and remove the skin of the tubers using a knife.
In a large pot of pan, add enough water to cover the tapioca tubers, add salt and bring the water to a boil.
Let the water boil for about 2 to 3 minutes.
Now drain the water and add fresh water to the pot to cover the tapioca.
Add more salt and bring the water to a boil again.
Cook the tapioca in boiling water for about 10 to 12 minutes or until the tapioca is cooked and soft.
Once the tapioca is cooked, drain the water and wait for the cooked tapioca to cool down.
Once the tapioca is cooled enough, slice lengthwise first, so you can easily remove the long string that pass through the middle of the tubers.
Remove the strings and cut the tapioca in small to medium sized cubes and keep aside.
Heat 2 tablespoons of oil in a very large pan and add mustard seeds.
When the mustard seeds splutter, add the curry leaves and red chilies, fry for a few seconds.
Add the chopped pearl onions to the pan, saute for about 2 minutes.
Add salt to the onions and stir fry the onions for another 4 to 5 minutes until the onions are softened and lightly browned on sides.
Meanwhile grind the coconut coarsely in a food processor (without adding any water or sprinkle a little water if necessaralong with enough salt, cumin seeds and green chilies, keep this mixture aside.
Add the cooked tapioca to the same large pan with pearl onions, stir everything well. You can gently mash the tapioca using a spoon or spatula at this point just enough according to the consistency you prefer.
Add the coconut mixture to the pan, add the turmeric powder and red chili powder to the pan and stir well to combine.
Sprinkle little water (about 1/4 cup), close the pan with lid and cook in low heat for about 3 to 4 minutes.
After 3 to 4 minutes of cooking, open the pan, and check the salt, if needed you may add more salt at this point. If adding more salt, stir well everything.
Add garlic powder to the cooked tapioca coconut mixture (if using fresh garlic, add it early along with the pearl onionand also the remaining 2 tablespoons of coconut oil to the tapioca coconut mixture, stir everything well. Cover and cook the contents for another 1 to 2 minutes in very low heat.
Open the pan after 2 minutes, stir everything well. Switch off the stove and keep the pan away from heat.
Cover the pan with lid and keep it closed for another few more minutes, which will make the kappa puzhukku or mashed tapioca coconut dish more delicious.
Serve the mashed tapioca hot with rice and curries or serve it as it is for lunch or dinner!