Ingredients:

plain yogurt - 1 1/2 cups (beaten)
squash - 1
black gram (urad dal) - 1 tsp
grated coconut - 2 tbsp
corn flour - 2 tbsp
green chillies - 5 medium-sized (adjust according to taste)
currry leaves - 1 stalk
cumin seeds (jeera) - 1 tsp
carom seeds (ajwain) - 1 tsp
ginger - 1 inch piece (or 1 tsp ginger paste)
turmeric powder - a pinch
oil - 1 tsp
mustard seeds - 1 tsp
coriander/cilantro leaves - a few
salt - 1 tsp (adjust as per taste)

Method:

Soak coconut, carom seeds and cumin seeds in warm water for 5 minutes. Blend with the ginger and green chillies into a coarse paste in a food processor. Cut squash into cubes. Take oil in a sauce pan and add mustard seeds, black gram and curry leaves. When it splutters, add squash, coconut mixture and half a teaspoon of salt. Cook until soft.  Add 1 cup of beaten yogurt, corn flour, turmeric powder and the remaining salt. Boil for a few minutes. Finally, add the remaining yogurt and remove from fire when it just starts to boil. Garnish with fresh coriander/cilantro leaves. Serve hot with rice / chapati / tortillas.

Notes:
If the final blob of yogurt is boiled in the mixture for a long time, the gravy will become very dilute.