On low heat, cook spinach and fenugreek leaves with a pinch of salt in 4 tablespoons of water, until wilted. Let it cool. Puree and keep aside.
Heat a pan and dry roast cumin seeds for a minute. Add pureed onion and 2 tablespoons of water and cook on medium heat, till the onion turns a light brown. Add pureed tomatoes, ginger-garlic-chilli paste and cook for about 3 minutes. Now, add powdered masala and simmer for about 3-5 minutes. To the mixture, add pureed spinach-fenugreek leaves, kasuri methi and 1 cup soy milk and allow to simmer until you obtain a medium-thick gravy.
Add steamed cubed sweet potato and allow to simmer in the gravy for about 5 minutes. Add salt to taste. Garnish with coriander leaves.