Heat the oil in a very large pan over a high heat. Put in the asefetida and then the spinach. Stir together.
Add the turmeric, cayenne, salt and bicarbonate of soda. Cook and stir until the spinach has wilted.
Add 2 cups of water and cook uncovered, stirring occasionally, over a medium high flame for about 25 minutes or until just a little liquid remains.
Reduce heat to low and mash the spinach with the back of a spoon.Continue to cook uncovered for a further 10 minutes. then sprinkle garam masala over the top and mix.