Pick the leaves along with some part of the stem (tender part) and wash them well. Immerse the leaves, for half an hour, in water to which about a couple of tsps of salt has been added. This ensures that any micro-level critters are taken care of! Drain the water out and rinse the leaves a couple of times.
Lightly steam cook or microwave the spinach leaves with very little water. Usually, turmeric is added to the spinach leaves while cooking. I prefer to add my turmeric much later as it keeps my Mashiyal a nice bright green colour rather than a slightly yellowish green. The taste is much the same and its just a matter of preference. Also turmeric acts as an antiseptic.
Let the spinach cool and then mash them well. Alternately, break down the leaves using a hand blender. Traditionally, the leaves should not be pureed fine but have a bit of texture to them. I prefer mine pureed.
Put the mashed spinach into a pan and place it on the stove top. Add salt to taste and turmeric and just bring to a boil and then let it simmer for 2 to 3 minutes. Take it off the heat. Transfer the Mashiyal into a serving dish.
In a small pan, heat the sesame seed oil and add the mustard seeds. When they splutter, add the black gram lentils. Stir till they start browning and then add the red chillies and the asafoetida powder. Do not let it burn. Stir once or twice and pour the tempering into the mashed spinach.
Stir well and serve warm as a side dish with rice.