Mashed potato mixture will turn sticky if boiled potato has excessive moisture. If mashed potato has excess moisture, cook it in a non-stick pan until excess moisture evaporates. Transfer it to a bowl, let it cool for few minutes and then add tempering and mix properly. Add 1/2-teaspoon cumin seeds and 1/4-teaspoon urad dal with mustard seeds for variation. If you want to make them in large quantity, prepare the vadas in advance and deep fry them again at the time of serving for crispy outer layer.