Heat the oil in a saucepan on medium high heat. Test the heat by adding one cumin seed to the oil; if seed cracks right away, oil is ready.
Add the asafetida and cumin seeds. After the cumin seeds crack, add red chilies stir-fry for few seconds.
Add spinach, salt, and black pepper and stir-fry, pressing the spinach down to allow most of the water to evaporate but still leaving the spinach moist.
After the spinach cools off, mix it well into the yogurt.
Add milk to the raita about half a cup adjust to the desire consistency.
For best result serve chill.