Combine garam masala, Ground coriander, chili powder, ground turmeric, ground cumin, and salt together in a small bowl. Set aside.
Cut cauliflower and potato into medium sized cubes and thoroughly wash it. Put in bowl. Set aside.
Heat oil in a frying pan / kadai. Add green chilli, ginger garlic and stir for few seconds.
Add chopped onions and fry over medium heat until light golden brown.
Add coconut milk, spice mixture, and the cauliflower and potato. Stir well. Cook uncovered for five minutes Cover the pan / kadhai and cook over medium heat until tender. Occasionally stir it to prevent sticking to the bottom.