- Preheat the oven to 180C/350F and line a large baking tray with grease proof paper.  
- Place the oil, sugar, egg and vanilla extract into a large bowl and whisk until well combined and slightly frothy. 
- Add in the melted chocolate and mix until everything is well combined. 
- Add in the flour, cocoa powder, baking powder and salt and mix until there are no lumps of flour and everything is smooth and combined. 
- Tip the batter onto your prepared baking tray and spread with a small angled spatula to 1/4-1/2 inch thickness. If you don't have large baking trays, I would advise you split the mixture between two smaller baking trays to ensure the Brownie Brittle is thin enough. 
- Once spread, sprinkle the batter with chocolate chips. Place in the oven for 20-25 minutes, until the top is crackly and firm to the touch and the edges are crisp. Mine, at 1/4 inch thickness, took 23 minutes. If you're using two trays, keep a close eye on it and check around 15 minutes. 
- Remove from the oven and score with a pizza wheel/long knife. I cut diagonally both ways and ended up with around 24 pieces, 2 inches across. Leave to cool before breaking up into pieces and enjoying. 
- Brownie Brittle will keep in an airtight container or Ziploc bag, at room temperature for 2 weeks.