Gather all ingredients. Preheat oven to 200°F (400°C). Set two wire racks atop paper towels.

Fill a large bowl with ice water. Using a mandoline with a waffle blade set to 1/4-inch, slice potatoes crosswise, then rotate 90° and make another slice for each waffle fry.

Add cut waffle fries to the ice water as they are done.

In a large heavy saucepan, add 2 inches of oil. Clip a candy/oil thermometer to the side of the pan. Heat oil over medium heat to 310°F (155°C).

Drain waffle fries and blot dry with paper towels.

Working in batches, fry waffle fries for 4 to 5 minutes. They should just cook through at this point, but not brown.

Remove from oil with a slotted spoon and place on wire racks.

Increase oil temperature to 375°F (190°C). Add waffle fries in batches and cook for 1 to 2 minutes until golden brown.

Drain on paper towels, sprinkle with salt, and transfer cooked fries to the oven to keep warm while frying remaining waffle fries.

In a small bowl, whisk together mayonnaise, ketchup, pickle brine, and Sriracha sauce to make the dipping sauce.