Preheat the oven to 280 C. Lightly spray the baking tray with cooking spray and line it with parchment paper. Spray the parchment paper.
In a medium bowl, combine the sugar, flour, melted white chocolate, powdered sugar, butter and baking powder
In a large bowl, whisk together the eggs and vanilla.
Sprinkle the dry mix over the wet mix and stir until just combined.
Pour half the batter into the prepared baking tray and then randomly drizzle the nutella over the mixture and give it a light mix and then again pour the other half and use a spatula to smooth the top.
Bake for 40 to 48 minutes, or until a toothpick comes out with only a few crumbs attached
Once out of oven, let it cool for sometime
Cut into squares and drizzle with Nutella and serve.