Grind coconut, green chillies, cumin and turmeric along with 1/2 cup water to form a fine paste and keep aside
Blend yogurt along with 1/2 cup water and salt until smooth
Keep aside
Cook the plantain pieces in little water along with salt, 1/4 tsp turmeric powder and 1/2 tsp red chilly powder until soft
Add the coconut paste to the cooked plantain and mix gently
Allow it to cook for 4-5 minutes
Reduce flame to low and add beaten curd
Heat it for a few minutes and remove from stove top
Be careful not to boil the curry after adding curd
Heat oil in a pan and splutter mustard seeds
Saute shallots, dry red chillies and curry leaves for a few minutes
Add 1/4 tsp red chilly powder and 1/4 tsp fenugreek powder and saute for a minute
Pour the seasoning over the curry and mix gently