Scrub potatoes clean if dirty and rinse under running water. Remove and discard any nubby sprouts. Place the potatoes in a large Dutch oven.
Fill the pot with water until the potatoes are submerged and covered by 1 inch of additional water. Add 1 tablespoon of the salt. Bring the mixture to a boil over medium-high heat and continue cooking until the potatoes are very easily pierced through by a fork (smaller potatoes are done around 20 minutes, and medium around 25 minutes).
While the potatoes cook, preheat oven to 425 F and drizzle 1 tablespoon of the canola oil over a large, rimmed baking sheet. Brush the oil so it’s evenly distributed over the sheet.
When the potatoes are done, drain in a large colander and let them cool for about 5 minutes, until they can be handled safely.
Evenly distribute the potatoes over the prepared baking sheet, and use a potato masher or a serving fork to gently smash each potato to a height of about ½ inch.
Drizzle remaining 3 tablespoons of oil over the smashed potatoes. Sprinkle the garlic powder, onion powder, paprika and remaining ¼ teaspoon salt over the potatoes. Finally, sprinkle them lightly with freshly ground black pepper.
Bake until the potatoes are nice and golden on the edges, about 25 to 30 minutes.
Serve sprinkled with chopped parsley and enjoy on their own as a snack or with your favourite dip.