Heat the oil in a large saucepan over a medium high heat. When hot add the onions. Fry, stirring, for about 3 minutes.
Add the spinach, chilli, ginger, salt and sugar. Stir and cook for 5 minutes.
Add the water and bring to a simmer. Cover tightly, turn heat to low and cook for about 10 minutes then uncover and boil away some of the excess liquid.
To serve sprinkle with the garam masala and mix well.