In a large microwavable mug add the Nutella and egg and whisk together.
Add flour and mix until you have a smooth batter.
Microwave for roughly 45 seconds – 1 minute. (Cooking time is based on my 1200W so your timing might vary). Always keep a close eye on your mug while in the microwave so it doesn’t overflow or overcook.
When the brownie is set and firm on top it is done. Let the brownie cool and minutes before serving
Serve with some vanilla ice cream while it’s still warm.