For the fries: Fill a large Dutch oven or a heavy bottomed saucepan two-thirds of the way with the oil. Heat over medium-high heat to 350 degrees F. Line a baking sheet with a wire rack.
Add 2 quarts water with 2 tablespoons salt in a large pot and bring to a boil. Add the potatoes, bringing the water back to a boil, and cook, about 5 minutes. The potatoes will be soft on the outside while still firm in the center. Drain in a colander and add to a large bowl to toss with the cornstarch and a heavy pinch of salt.
Add the potatoes to the hot oil a few at a time, stirring and flipping constantly until they are golden brown on all sides, about 4 minutes. Remove to the wire rack, sprinkle with salt and repeat with the remaining potatoes.
For the pimento aioli: Add the mayonnaise, pimentos, red wine vinegar, garlic, chipotle and paprika to a food processor and blend until smooth.
Add potatoes to a serving bowl and serve with the aioli drizzled over the top and on the side for dipping.