Preheat oven to 450 degrees. Line a baking sheet with tinfoil.
In a small bowl mix together butter, olive oil, rosemary, nutmeg, salt and pepper.
Create hassleback cuts: slice each potato into thin slices, leaving 1/4 inch at the bottom unsliced.
Place potatoes on a baking sheet and generously brush on the rosemary butter, making sure to get in between all the individual slices.
Bake until tender and crisp, 55 minutes.
Serve with additional toppings of rosemary butter, sea salt and fresh rosemary.