Soak the cow peas overnight. Drain, dry roast and and pressure cook it until soft - about 2 whistles. Set aside.
Cut the tubers into large cubes. If using pre-cut vegetables ensure that all are cut into roughly equal size pieces. Cut raw plantain into slightly smaller pieces. Add all the vegetables into the pressure cooker, along with turmeric, curry leaves , chili powder and half the salt. Add enough water to barely cover the vegetables. Pressure cook for just 1 whistle. Let the pressure release naturally.
Grind the coconut with garlic and cumin seeds into a rough paste adding 1 to 2 tbsp of water as necessary.
Open the cooker and and check the vegetables - they must be cooked and firm. There should be just a little water at the bottom , but not a lot. If there is excess moisture cook with the lid open to evaporate most of the water. Add the cooked beans along with the coconut paste. Stir and adjust salt as needed. Turn the heat on to medium and bring the mix to a slow simmer - stirring a few times to prevent the mix from sticking to the bottom. Cook on low heat for a few minutes until the raw smell of garlic fades.
Turn off the heat. Crush a few curry leaves by hand and place on top of the puzhukku. Drizzle a little coconut oil on top and cover with the lid. Keep covered till serving.
Use available root vegetables to make up the quantity.
Horse gram, Green Gram and White beans are the other beans used in place of cow peas in this recipe.
A small piece of pumpkin can be used in place of sweet potato.
For a spicier version add green chilies while grinding coconut.
For detailed instructions go to https://oventales.com/thiruvathira-puzhukku/ .