Adjust oven rack to lowest position and preheat to 475 degrees. Place minced garlic cloves in a small bowl and pour in 2 tablespoons of oil. Set aside.
Place potato wedges in a large bowl and cover with hot water. Let potatoes sit in water for 10 minutes. Drain and dry thoroughly with paper towels. (Very thoroughly! This is important.) Rinse and wipe out bowl.
Grease a heavy-duty rimmed baking sheet with remaining tablespoon of oil. Return potato wedges to bowl. Use a fork to remove the garlic from the oil; discard garlic. Drizzle oil over potatoes and toss to coat.
Arrange potato wedges on baking sheet in a single layer. Sprinkle with salt and pepper. Tightly cover baking sheet with foil; bake 5 minutes. Remove foil, then bake 10-15 minutes or until bottoms of fries are golden brown. Use a spatula or tongs to flip each wedge, then cook 5-10 minutes more until fries are browned.
While fries are baking, make harissa ketchup by stirring together ketchup and harissa in a small bowl.