Avial – a mixed vegetable curry in a spiced coconut and yogurt sauce, is a very quintessential Kerala dish that is made for Sadya (a feast)! It also features very regularly in everyday meals in Kerala.
You can use other vegetables like the small eggplant, other squashes or melons etc. This is usually the combination I use.
Yogurt is used as the souring agent here. In certain parts of Kerala, tamarind is used as the souring agent instead. If using tamarind, use a lime sized ball, soak in water and take out the pulp. Add this to the vegetables when they are cooking. Skip the yogurt. Grind the coconut with a little water instead.
If using frozen coconut, microwave the frozen grated coconut for 30 secs or so. This way the coconut seems to grind better without having fat solids stuck in the mixer/food processor.