Heat the oil in a saucepan. Add the onions and stir fry until they just start to brown.
Add the garlic, chillies, sage and cilantro and stir for a few seconds. Now add the pumpkin cubes.
Add 1/4 cup of water or vegetable stock and when the water begins to simmer, turn the heat to low, cover the saucepan and let the pumpkin cook, stirring occasionally, for about 45 minutes or until it is buttery-soft and tender. Mash some of the pumpkin cubes, if you like, for more texture.
Add salt and sugar and turn off the heat. Serve hot with rotis or as a side dish with rice and a spicy curry.