Preheat an oven to 350F. Spray a jumbo muffin pan with cooking spray or line with muffin liners.
In a mixing bowl, whisk together the flour, sugar, cocoa, baking powder, baking soda and salt.
Make a well in the center and add the eggs, sour cream, oil and nutella. Stir together until just combined.
Fold in the chocolate chunks and chips. Use a spoon or ice cream scoop to fill muffin cups 3/4 full. Bake in preheated oven for 20-25 minutes, or until an inserted toothpick comes out clean. Let cool on wire racks.