Heat oven to 400 degrees. Place a heavy baking sheet in the oven. Scrub and rinse potatoes well, and then cut them lengthwise into 1/2-inch-wide batons. Place potato batons in a medium bowl, and toss them with olive oil, salt, and pepper.
When baking sheet is hot, about 15 minutes, remove from oven, and spray with olive-oil cooking spray. Place prepared potatoes on baking sheet in a single layer. Return to oven, and bake until potatoes are golden on the bottom, about 30 minutes. Turn potatoes over, and continue cooking until golden all over, another 15 minutes. Serve immediately, with malt vinegar, if desired.