Preheat oven to 450 degrees. Generously grease a large baking sheet. Boil halved potatoes in a large pot for 6-8 minutes, or until barely tender.

Rinse potatoes under cold water. Drain and pat dry with paper towels. Gently rake the rounded side of the potatoes with a fork to create ridges.

Place the potatoes in a large bowl, set aside. In a small bowl whisk together butter, olive oil, garlic and rosemary. Pour over potatoes and toss to coat well. Season with salt and pepper, to taste.

Arrange the potatoes, cut side down, on prepared baking sheet. Bake for 25-30 minutes, or until golden brown. Turn potatoes once during baking, if desired.

Re-season with salt and pepper if needed and garnish with fresh parsley before serving.