Create the Flavor Paste: In a blender or food processor, combine the lemon juice, onion, garlic, ginger, crumbled red chili, and ground cumin.
Blend until you have a completely smooth paste, scraping down the sides as needed.
Prep the Potatoes: Peel the potatoes and slice them lengthwise into thin ⅛-inch / 3mm slices. A mandoline is your best friend here for uniform cuts! Stack the slices and cut them again into matchsticks of the same thickness. To ensure maximum crispiness, place the cut potatoes in a bowl of cold water, then drain and pat them completely dry before frying.
Fry to Golden Perfection: Pour about a ½-inch / 1. 3 cm depth of oil into a large frying pan or skillet over medium heat.
Once the oil is shimmering hot, carefully add a single layer of potatoes.
Fry in batches, stirring occasionally, until they are beautifully golden and crisp. Use a slotted spoon to transfer them to a paper towel-lined plate to drain.
Toast the Spices: Carefully pour out all but 4 tablespoons (60 ml / 2 fl oz) of oil from the pan.
Add the sesame seeds to the hot oil and stir until they begin to pop and become fragrant. Immediately pour in the onion-ginger paste.
Stir and fry over medium-low heat until the paste has browned, dried out, and is incredibly aromatic. This step is key to developing the deep flavor!
Combine and Serve: Add the crispy fried potatoes back into the pan with the spice paste.
Sprinkle with salt, pepper, and sugar. Gently toss everything together, breaking up any clumps of the spice mixture to ensure every single potato is coated in deliciousness.
Serve immediately while hot, or enjoy at room temperature.
Don't overcrowd the pan when frying.
Cooking the potatoes in batches ensures they fry evenly and get perfectly crisp rather than steaming.