Heat a pan with oil, once the oil is hot add the cumin seeds,mustard+ urad dal, channa dal and saute for a few minutes. Then add dry red chillies, crushed garlic and fry for a few seconds.
Add finely chopped onion, a few curry leaves and saute for a few minutes until the onion turns translucent.
Next, add the chopped potatoes and mix well.
Add turmeric, coriander, red chilli powder, salt and mix well with potatoes, without burning the spices.
Cover and cook on medium heat for 6-7 minutes or until the potatoes are 90% cooked. Open the lid in between and stir them otherwise they will stick to the pan. Don't overcook them.
Add chopped spinach in batches and mix well. Cook for 3-5 minutes until all the spinach is combined well with the potatoes.
Finally, add garam masala and switch off the heat.
Serve the stir fry with roti or rice and dal