• Preheat the oven to 350°C (180°C). Mist and 8-inch square brownie pan with cake release and line with baking paper.
• Add the chocolate and butter in a mixing bowl and microwave for 30 second bursts until the butter melts. Leave to stand for a couple of minutes then stir so that the chocolate melts completely. Set aside.
  1 ¼ cups (200g) chocolate chips, ½ cup (115g) unsalted butter
• Use a hand mixer to beat the sugar, eggs, vanilla and salt in a separate bowl. Whisk until the sugar is dissolved and the mixture is pale and doubled in volume.
  1 cup (200g) sugar, 2 large eggs, 2 tsp vanilla bean paste, ¼ tsp salt
• Pour the melted chocolate mixture into the beaten eggs and stir to combine.
• Sift the flour, cocoa powder and salt into the bowl and stir until you have a smooth, glossy, thick batter with no dry pockets of flour.
  4 tbsp cocoa powder, ½ cup (65g) flour
• Spoon the batter prepared pan and level. Bake for 25-30 minutes. A toothpick inserted in the middle should come out with a few moist crumbs (but not wet batter). Leave in the pan to cool down slightly.

Make the filling

• Use a sharp knife to roughly up the Ferrero Rocher truffles until you have small pieces with some chunkier bits.
  20 Ferrero Rocher hazelnut chocolate truffles
• Prepare the filling as the brownie cools down. Place chocolate chips and hazelnut spread into a mixing bowl and microwave for 20 -30 second bursts until the the chocolate starts to melt. Stir well until smooth and set aside while you make the base.
  1 cup (300g) hazelnut spread, ½ cup (80g) chocolate chips

Make the brownie roll base

• Break up the brownie into small pieces, add to the bowl of a stand mixer fitted with the paddle attachment and beat until the brownie clumps together. Alternatively simply break up the brownie into small crumbs using your hands.
• Line a sheet pan (9x13 inches) with baking paper letting the edges overhang. Tip the brownie mixture into the pan and use your hands or small roller to press down into a firm even layer.

Roll into a log

• Lift the brownie base out of the pan using the paper. Spread the filling to cover the base leaving small border on the edge furthest away from you. Scatter with the chopped Ferrero Rocher, pressing them down slightly.
• Start rolling the brownie from the short end closest to you using the paper to aid you. Press down firmly with your hands as you roll into a log. Wrap tightly with plastic wrap (cling film) and chill until set.

Decorate and serve

• Melt the chocolate in the microwave or a double boiler and stir in the vegetable oil. 
  1 cup (175g) chocolate chips, 2 tbsp vegetable oil
• Pour the chocolate over the brownie yule log to cover – it will drip easily down the sides so you may want to position the log over a wire rack with a tray underneath to catch any chocolate drips. 
• Sprinkle the brownie roll with chopped hazelnuts while the glaze is still wet and leave to set.
  2 tbsp chopped hazelnuts
• Run a large knife under hot water and dry. Use the knife to cut the brownie roll into slices and serve!