Leave skins on, rinse potatoes and remove all dirt. Cut into slices, all the same thickness. The thinner they are the crispier they will get.
Fill a bowl with cold water and submerge your slices. Cover bowl and put into fridge for 2-3 hours ideally (optional step but if you want them as crisp as possible this is what is needed)
Lay potato slices on paper towels and gently press down to remove all moisture from the outsides. This will get them crisp! Slice 1/2 an onion into slices.
Preheat skillet over medium heat and add 2 tablespoons oil. Add potatoes and drizzle remaining 1 tablespoon vegetable oil on top with garlic. Mix well to coat potatoes. Sprinkle with seasoning and mix well to coat.
Cover and continue to cook over medium heat for 7 minutes. Do not stir while covered. Remove lid and add onions, stir to mix well. Cover and continue to heat (without stirring) for an additional 7 minutes.
Remove lid and continue to cook 1-2 minutes more or until tender to your liking on inside.