Preheat oven to 400ºF. Spray a standard muffin pan with non-stick cooking spray, or line with paper liners.

In a large bowl, whisk together the flour, cocoa powder, hot chocolate powder, baking powder, baking soda, instant espresso, and salt until combined; set aside.

In another bowl, use a fork to combine both sugars and the eggs together until thickened and combined, about 45 seconds. Stir in the oil. Add the sour cream and vanilla, and continue mixing until combined.

Toss the chocolate chips into the flour mixture. Using a rubber spatula, gently fold the wet ingredients into the dry ingredients until just combined. Place a spoonful of batter into each muffin well, creating a little dent in the center. Fill dent with a dollop of Nutella, then cover it up with more batter. Sprinkle with more chocolate chips, if desired.

Bake for 15-18 minutes, or until a toothpick comes out with few moist crumbs attached. Allow to cool in the pan for 10 minutes before serving.