Soak the beans overnight. If fresh cowpeas are in season, use that and no soaking is required.
In a pressure pan / cooker, place the drained beans. Top with 1 cup water, salt and turmeric. Pressure cook for 1 whistle and then on sim for 5 minutes.
Once the cooker is cool enough to open, add the pumpkin pieces to the cooked beans. Add 1/4 cup water if required and pressure cook this for 1 whistle. (This is because the beans have a slightly longer cooking time than the pumpkin. I used fresh cowpeas so pressure cooked it with pumpkin for one whistle.)
Open the lid of the cooker. Mash the beans and pumpkin lightly with the back of a ladle.
In a mixer jar, grind the chili, coconut and cumin to a smooth paste using 1-2 tbsp of water.
Add this to the cooked pumpkin-beans mix in the cooker. Bring to a simmer. Add 1/4 tsp salt if required. Remove into a serving bowl.
Heat the oil in a small pan. Add mustard seeds. Once it splutters, add the curry leaves and red chillies. Add the desiccated coconut to this and roast until it is aromatic and golden brown and transfer this over the erissery.