Step 1

Preheat the oven to 170C/150C Fan/Gas Line a 30x20cm/12x8in straight sided brownie tin with foil or non-stick baking parchment.

Step 2

Sieve the flour, cocoa and baking powder together in a bowl and add a good pinch of salt. Break 250g/9oz of the chocolate into a heatproof bowl and place over a barely simmering saucepan of water, making sure the bowl does not touch the water. Leave to melt, stirring regularly.

Step 3

When the chocolate has melted, remove and leave to cool slightly. Roughly chop the remaining chocolate and set aside.

Step 4

Beat the butter and sugar together in a bowl until very light and fluffy. Add the eggs, one at a time, then pour in the chocolate. Mix thoroughly, then add a third of the flour mixture. Stir to combine, then repeat with the other two-thirds of flour.

Step 5

Add half of the hazelnuts and all the reserved chopped chocolate and stir to combine, then scrape the mixture into the prepared tin.

Step 6

Whisk the chocolate spread and hazelnut liqueur together (if using), until you have a smooth, spoonable paste. Make little wells in the brownie mix and add spoonfuls of the mixture.

Step 7

Sprinkle over the remaining hazelnuts and press down lightly. Bake in the preheated oven for around 30 minutes, testing after 25 minutes. When the brownies are done a wooden skewer should come out with a few crumbs attached – it shouldn’t be wet, but it shouldn’t be completely clean either.

Step 8

Leave to cool in the tin. If you can bear to wait, put the brownie tin in the fridge to rest overnight before cutting them – it will help them settle into a consistency that isn’t too cake-like. Cut into squares and store in an airtight tin.