1. Preheat oven to 360F (180C). prepare muffin tin lined with muffin paper cups.
2. Into a bowl sift bowl flour, cocoa powder, baking powder, baking soda and salt. Set aside.
3. In a large bowl cream butter and sugar, add oil and beat until combined. Add egg and vanilla extract. Beat until combined. Add buttermilk and mix until combined.
4. Add flour mixture to wet ingredients. Mix until combined and smooth.
5. Divide the batter evenly between 12 muffin cups, filling only half way. Pipe 1-2 teaspoons of Nutella in the center (or use spoons). Then spoon the remaining batter on top. Sprinkle chocolate chips on top.
6. Bake for 20-25 minutes or until an inserted toothpick comes out clean. Let cool on a wire rack.