Melt chocolate and butter in the microwave, in thirty-second intervals and stirring in between until it is completely melted and mixed.
In a medium mixing bowl, whisk the eggs and sugar until light and fluffy. Add chocolate mixture into the eggs. Add flour and mix until incorporated.
Grease 6 cupcake/muffin molds. Fill each about 3/4 full with batter. Then put a generous tablespoon of Nutella in the middle of each.
Bake in a pre-heated oven at 350°F or about 10-12 minutes. The cake should be cooked on the sides but still gooey in the center.
Remove cakes carefully and turn upside down onto plate. You may need to use a knife gently along the sides of the muffin molds. Serve while warm.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.