Set oven to broil.

Place eggplant, jalapeños, and onions onto an aluminum foil-lined baking sheet. Drizzle the oil and sprinkle half the salt over the vegetables. Broil for 12 minutes.

Remove jalapeños from tray, flip the eggplant and onions, and broil for an additional 10–12 minutes, until charred on both sides.

Meanwhile, remove seeds and membrane of the jalapeños according to your taste — the heat is in the seeds and membrane, so leave more or less depending on your preferred heat level. Allow all vegetables to cool.

Place all vegetables, along with remaining salt, sugar, and mayonnaise in the bowl of a food processor. Blend for a couple of minutes, until completely smooth. Store in fridge until ready to use, up to a week.

Boil whole potatoes in salted water for about 20–30 minutes, until fork-tender (depending on the size of the potato). Drain potatoes and set aside to cool.

Slice each potato thinly. Heat a thin layer of oil in a large frying pan over medium-high heat, and place potatoes in a single layer into the pan. Fry for about two to three minutes per side, until crispy and golden brown. Remove from pan and sprinkle with salt to taste.