Line a 15- x 10-inch jellyroll pan with aluminum foil; coat foil with cooking spray.
Toss potato with 2 tablespoons olive oil, and place in prepared pan.
Bake at 450° for 30 to 40 minutes or until potato is tender. Place in a large bowl; stir in green onions and sesame seeds.
Whisk together champagne vinegar and next 4 ingredients in a small bowl; gradually whisk in 1/3 cup olive oil and sesame oil. Pour over potato mixture, and toss gently. Garnish, if desired