Peel the potatoes and use a mandoline slicer if you have one to cut the potatoes into uniform size sticks. This is important and will make your life easier when you fry them. They are cooked and get crispy at the same time. You can manually cut them too, it's more work!
Soak the potato sticks in fresh cold water for at least 2 hours (overnight is fine too) and then drain off all the water and starch that leaks out. Do not skip the soaking part
Use an absorbent paper towel and pat the potatoes dry
Fry the potatoes:
Preheat about 1 1/2-inches of cooking oil over high heat. When you dip a chopstick into a oil and it bubbles around the chopstick, the oil is ready. Or you can just put one piece of potato in there and if it bubbles and floats, the oil is ready. Lower the heat to medium
You need to fry the potatoes in 3-4 batches. DO NOT dump all at one go. Place the first batch in and fry until the potatoes are crispy and golden brown. Remove to an absorbent paper towel. Continue frying the next batch.
Prepare the spiced paste:
Place all ingredients for the spiced paste in a bowl, except for kaffir lime leaves and bay leaves
Preheat 1 Tbsp of cooking oil in a large pan/wok. Add the kaffir lime leaves and Thai chili and fry briefly, about 10 seconds or so. Add the rest of the ingredients above and bay leaves and cook until the sauce thickens to a syrup consistency
Add the fried potatoes into the sauce and turn off the heat. Stir to make sure the sauce is coating the potatoes. Sprinkle in the bawang goreng and stir again to mix. Transfer to a serving bowl
Kering kentang is best served on the same day. The kering kentang will stay crispy for one whole day. The next day, they will get significantly soggy, which is normal as the moisture from the sauce continues to soften the potatoes