Slice potatoes in wide rectangular slices about 1/4-inch thick and 3/4-inch wide, yielding 12 to 15 slices per potato. Keep potatoes in cold ice-water bath until ready to fry.

Heat oil in a deep-fryer or large saucepan to 350°F (175 degrees C)

Set oven rack about 6 inches from the heat source and preheat the oven's broiler.

Dry potato slices on paper towels.

Fry potatoes in hot oil for 1 minute; remove from oil, drain, and set aside to cool for about 10 minutes. Return potatoes to oil and fry until golden brown, about 5 minutes more. Again, remove from oil and drain briefly on paper towels.

Spread potatoes onto a baking sheet; top with Cheddar cheese, Monterey Jack cheese, and bacon.

Heat the fries under the broiler until the cheese melts, 3 to 5 minutes. Top with jalapeno peppers to serve with ranch for dipping.