Wash potatoes and peel. Cube to small bite sizes about half inch cubes. Keep them in a bowl of water until used. This helps to remove the excess starch and prevents them from sticking to each other while frying.
Crush or chop garlic. Rinse curry leaves and set aside.
Pour oil to a heavy bottom non stick or cast iron pan. When the oil turns hot, add cumin, mustard, red chili and dal (optional). Fry until the dal turns golden.
Add curry leaves and garlic. When the garlic is lightly fried, add hing.
Drain the water from potatoes and then add them to the pan. Sprinkle turmeric. Mix and fry potatoes for about 3 to 4 minutes on a medium heat stirring often.
For crispy aloo fry, keep stirring and fry them without covering until fork tender. You can also add more oil for better roasting.
For soft potatoes, lower the flame. Cover and cook till the potatoes are fork tender. Stir in between to prevent burning.
When the potatoes are done, prick them with a fork to check if they are cooked completely. You shouldn't feel them hard from inside. Otherwise cook them for a little longer.
Then sprinkle chili powder, salt and garam masala. Toss everything well and fry for a minute or two to blend well. I usually add a tsp of oil at this stage so the spice powders coat all of the potatoes easily.
Serve potato fry with rice and rasam, sambar.