Cut the potatoes into 1/2-inch thick sticks. Place into a large bowl and cover completely with cold water for 15 minutes. Drain well and pat dry with a towel before frying. Heat the oil in a heavy bottom pan or pot to 300°F.
Add your fries to the 300°F oil and cook for 5-8 minutes, just until potatoes are starting to become soft but are not yet browned. Remove potatoes from oil and layout on a paper towel-lined baking sheet to drain excess grease. Increase the oil temperature to 375°F and return the potatoes to the oil. Cook until crispy and golden brown. Remove to a paper towel-lined baking sheet and season with salt to taste.
Place the fries on a foil-lined baking sheet, top with cheese. Place under the oven broiler until all the cheese has melted. Garnish with scallions and drizzle with ranch.