01 -
Preheat your oven to 175°C (350°F).
02 -
Line a 20 x 20cm (8 x 8 inch) baking dish with non-stick baking paper, allowing an overhang for easy removal.
03 -
In a medium-sized bowl, combine flour, rolled oats, salt, and baking soda. Mix well.
04 -
In another bowl, combine the melted butter, brown sugar, and vanilla extract. Mix thoroughly.
05 -
Add the wet mixture to the dry mixture and mix until evenly combined.
06 -
Press ¾ of the prepared mixture firmly into the baking dish, reserving about ½ cup (100 g) of the mixture.
07 -
Bake the base in the preheated oven for 10 minutes.
08 -
In a small bowl, combine Nutella and chopped hazelnuts. If Nutella is too thick, microwave briefly to soften.
09 -
Remove the base from the oven and immediately spread the Nutella and hazelnut mixture over it.
10 -
Crumble the reserved mixture over the Nutella layer using your fingers.
11 -
Return the dish to the oven and bake for an additional 10 minutes, or until the topping is golden brown.
12 -
Allow the bars to cool at room temperature for 30 minutes, then refrigerate for an additional 30 minutes until fully set.
13 -
Remove the slice from the dish using the overhanging baking paper. Cut into squares and serve.