Peel the banana and cut it vertically into half. Slice each halves into 1/4 inch thick pieces. Cook the sliced banana with chilli powder, pepper powder, turmeric powder and salt by adding required amount of water.
Add slightly beaten yogurt to this and cook until the yogurt gets thickened. Stir continuously to prevent curdling. (this is a time consuming process)
Grind together coconut, cumin seed, fenugreek and green chilly with little water to a smooth paste and add to the banana mixture, mix well. Cook for few minutes and turn off the heat. The gravy tends to thicken as it rests.
Heat ghee in a small pan and fry mustard seed, red dry chilly, curry leaves. Add this to the curry.