Boil potatoes in a pressure cooker. We will make dough for kachoris by the time potatoes are boiling.

Sift flour and semolina, add salt, baking powder and oil and mix well with hands.Knead soft dough with lukewarm water (like the one for making chapattis). Cover and keep aside for half an hour.

Peel boiled potatoes and break in small pieces. Heat oil in a small wok. Add cumin seeds in oil. When cumin seeds crackle, add coriander powder, green chilli, ginger, salt and potato. Stir fry for 2-3 minutes.

Make lemon sized balls from dough. Place one ball on your palm, flatten with fingers. Gently press the centre of the kachori with your thumb, add 1 to 1 ½ teaspoon of potato filling and seal the ends in shape of a Kachori. Press between palms. Roll gently with a rolling pin. 

Heat oil in a kadai for deep frying. Deep fry kachoris on medium flame. Turn while frying till they turn brown on both sides.
Place kachoris on napkin on a plate. Fry all kachoris.