Preheat the oven and melt the butter

• Preheat the oven to 350 °F.
• In a pan over low heat, melt the butter.
• Remove from the heat and let it cool for a minute or two so it is warm, not hot.

Whisk the sugars and eggs

• Whisk in the oil, granulated sugar and brown sugar for a full minute until glossy.
• Add the eggs, egg yolk and vanilla and whisk for another full minute until the mixture looks pale and slightly thick, this is what gives the crackly top.

Fold in the dry ingredients

• Sift in the flour, cocoa powder, espresso powder and salt.
• Gently fold until just combined, being careful not to overmix.

Layer the batter with chocolate and Nutella

• Fold in about half of the chocolate.
• Smooth half the batter evenly in the pan and spread a layer of Nutella on top.
• Pour the remaining batter on top and smooth it out.
• Sprinkle the remaining chocolate on top.

Bake the brownies

• Bake for about 25-30 minutes; the edges should be set and puffed and the center should look soft but not liquid.

Cool and slice

• Remove from the oven and let cool for at least 30-45 minutes so it can fully set before slicing.
• If you don't let it rest it will look raw but it should set.