Add egg and egg yolk to a medium mixing bowl. Mix with a whisk until smooth. Add in sugar and whisk until smooth. Add in Nutella spread and whisk again until smooth. Add in flour and whisk until smooth.
Grease two 4 oz porcelain ramekins with cooking oil spray (do not use the baking spray that has flour added). Divide batter evenly between the two ramekins.
Place trivet inside the inner pot of your Instant Pot and fill with 1 cup of water. (I use the 6 quart Instant Pot 7-in-1 Multi-Functional Pressure Cooker which requires 1 cup of water to come to pressure. It's my understanding that the larger version and other versions need different amounts of water so please add whatever the amount of water is stated in the instruction manual to allow the pot to properly pressurize).
Place ramekins onto trivet. Seal Instant Pot and set to manual, high pressure, 9 minutes.
When Instant Pot is done, do a quick release to prevent cakes from overcooking. Use tongs to remove ramekins from Instant Pot. Place each ramekin onto a separate coaster. This will allow you to invert the cake more easily while the ramekin is still hot. Place a small plate on top of each ramekin. Invert the ramekin by lifting the coaster with the ramekin and plate and gripping with both hands (like you're holding a sandwich) and flipping it upside down so the coaster side is now facing up and the plate is on a the bottom. Tap the ramekin a few times too loosen the cake. Cake should fall out inverted onto plate. Repeat with remaining cake. Dust with powdered sugar and serve with fresh fruit. Cakes are best enjoyed while warm.
If you don't have 4 oz ramekins*, you can also use 6 oz pyrex bowls*, which have the same bottom width as the 4 oz ramekins so that cooking time remains the same. I do find that the glass bowls don't cook quite as evenly as the ramekins though so I prefer using ramekins.
This recipe makes two cakes. If you want to make more, you can cook several batches. You can attempt to cook 4 at a time, using the same amount of water and time. You likely won't be able to fit four onto the trivet, so you'd have to place three on the trivet and balance one on top of the other ramekins.
*Some of the links contained in this post are affiliate links. Much like referral codes, this means I earn a small commission if you purchase a product I referred (at no extra charge to you).
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.