Add 3 tbsp of mustard seed oil to a wok or nonstick fry pan. Heat the oil on medium high heat.
Once hot, add the fenugreek, thyme seeds, and hing. Let the fenugreek get light brown and add the whole chili. Fry until the fenugreek turns dark brown.
Add the two potatoes (be careful of the oil spraying) and mix them in the oil. Then add the turmeric. Fry for 3 minutes with the lid on and stir occasionally.
Add the spinach and fry for 2 minutes (uncovered) while stirring regularly.
Add two cups of water and the salt. Put the lid on and let boil for 10 minutes.
Add the tomatoes. Continue to boil with the lid on for 4 minutes.
Using the back of a large metal spoon/cooking utensil mush the potatoes and the tomatoes. They should begin to dissolve into the sauce.
If the water has evaporated, you can add half a cup more, however if it still has enough liquid to be soupy, then it's not necessary to add any extra. Turn the heat down to low and simmer with the lid on for 6 minutes.
Turn off the heat and let sit for 3 minutes before serving.