Line a baking tray with non stick cooking paper and dollop 12 1 and ½ tablespoon blobs of Nutella on the tray and place in the freezer for half an hour.
Preheat the oven to 180°C (350°F) and grease and muffin tin.
Melt the butter and mix in the brown sugar.
Beat in the eggs and vanilla.
Mix in the flour, baking soda and baking powder.
Place half the mixture evenly between each of the 12 muffin tins.
Take a Nutella dollop and place one in the center of each.
Top each with the remaining blondie mixture.
Bake for around 12 minutes until the outside is golden.
The middle will sink and be wobbly but that is normal.
Notes
Eat warm for a delicious comforting treat. Allow to cool completely if you don't want the Nutella to spill out of the blondie or alternatively place in the fridge for 2-3 hours if you want a solid center.