Bengali Eggplant and Yogurt with Mustard Seed

Soak ground mustard seed and cayenne in one cup of water. Cut up eggplant into cubes. Heat mustard oil, put in panch pharon mix and after a few seconds add the black mustard/cayenne water. This will splatter so have a cover ready. Add eggplant and cook. You will probably need to add additional water as the eggplant cooks to keep its level about the same, perhaps another cup. Cover it for the last ten minutes. When the eggplant is cooked add a cup of yogurt and the salt, mix and heat up yogurt, but do not boil. Sprinkle a tiny bit of black pepper and cardamon over the top if you want. This dish also tastes good cold the next day. Variation: Make this without the yogurt, substituting green chillis for cayenne and using only fennel for the panch pharon mixture.