Add butter and chocolate chips to a large microwave safe bowl and microwave in 30 second intervals. Make sure to stir between each interval. It took me a minute and 30 seconds to get it completed melted and smooth. The last 30 second interval, I split into 15 seconds each, stirring in between. Once fully melted and smooth, add in powdered sugar and mix well. Next add in the egg and egg yolk and mix until completely combined together.
Lastly, add in flour and fold together until all ingredients are combined. Evenly divide the batter between 3 ramekins (if you have 6oz ramekins it will be 2). Bake on 400°F for 12-15 minutes. The edges will be firm and the center may be slightly soft. If using the toaster mode on the air fryer toaster oven, the top part may slightly brown, this is ok.
Remove from oven and let stand for 3 minutes. Take the end of a small spoon around the edges of the cake to help the cake to lift from the ramekins. Invert each ramekin onto a small plate and enjoy! Top with whipped cream, ice cream, chocolate syrup, fresh berries … whatever you like.