Preheat the oven to 200ºC/ Fan 180ºC/Gas 5 and grease and line a small baking tray about 25cm x 18cm.
Sift the flour into a mixing bowl, crack in the eggs and mix well with a wooden spoon. Scrape out the contents of a jar of Nutella and add this to the mixture, holding back 1 heaped tablespoon of the spread in a separate bowl.
Stir everything together until the mixture is smooth.
Pour the mixture into the baking tray, spread it out with a spatula and bake for 25 minutes. You’ll know they’re ready when they’re just set and starting to crack on top.
Don’t over-bake them as they will continue to cook in the tin and you want them to stay squidgy inside!
As the brownies cool, drizzle the remaining Nutella over the top to decorate. If it’s too solid, microwave it for 10 seconds in a heatproof bowl first. Slice into chunky squares or rectangles to serve.