Beat the butter, oil, sugar, eggs and vanilla in a mixer until blended
Mix the dry ingredients and stir them into the wet mix until combined.
Spoon the batter into a greased muffin cup or use paper liners. Fill approximately 3/4 full.
With a tablespoon, place a dollop of the Nutella on top of the batter. Swirl the spread with a toothpick or skewer so it looks marbled.
Bake at 425 degrees for 5 minutes. Then reduce the heat to 350 and continue baking for another 15-20 minutes or until a toothpick inserted into the muffin comes out clean.