Heat 2 tbsps oil in a non-stick kadai. Finely chop ginger and add along with green chillies and sauté for a minute. Reduce heat, add roasted chana dal powder and sauté for ½ minute.
Turn off heat and add ½ tsp amchur , red chilli powder, turmeric powder, roasted cumin powder and Punjabi garam masala powder. Turn on the heat again, add salt and sauté. Add sweet potatoes and mix well.
Transfer the mixture into a bowl, mix well and set aside to cool. Halve the dates, sprinkle lemon juice and ½ tsp amchur and mix well.
Mix corn flour and ¼ cup water in another bowl till smooth.
Transfer the sweet potato mixture in a parat and divide it into lemon sized balls, make a small dent in the centre, place some of the date mixture, bring in the edges and seal. Roll into a smooth ball and press lightly to shape into tikki.
Finely break the seviyaan and keep in a plate. Heat oil in anon-stick pan, dip the tikkis in corn flour batter, roll them in seviyaan so that they are well coated and place in the pan.
Shallow fry the tikkis, turning them, till they become golden brown on both sides. Drain on absorbent paper. Arrange them on serving plate, garnish with tomato slices and serve hot.