Combine potatoes and olive oil in ziploc bag and toss to coat. Arrange potatoes cut side down on baking sheet and cook for 20 minutes. Turn potatoes and cook 6 minutes. Cool 15-20 minutes. Use paring knife and cut a circle just inside of the edge of the cut side of the potato. Using a melon baller remove the guts of the potato and place in a bowl. What remains should be a shell.
Combine the pulp of the potatoes, sour cream, parsley, garlic powder, Gruyere cheese, salt and pepper. Mix until well combined. Add mixture back to the potato shells gently.
Sprinkle with green onions and bacon.
Place under the broiler for 2 minutes.
This is a small portion. If served as a full dinner side 3-4 potato halves would be appropriate.