METHOD

1. Preheat oven to 160°C (325°F). Line a 22cm round springform tin with non-stick baking paper. Place the butter and chocolate in a large heatproof bowl over a saucepan of simmering water (the bowl shouldn’t touch the water). Stir until melted and smooth. 
   
2. Place the eggwhites in the bowl of an electric mixer. Whisk on high speed until soft peaks form. Gradually add the sugar and whisk until thick. Scrape down the sides of the bowl and whisk for a further 2–3 minutes or until the mixture is thick and glossy. 
   
3. Add the egg yolks and salt to the chocolate mixture and whisk to combine. In 3 batches, add the eggwhite mixture to the chocolate mixture and gently fold to combine. Pour into the tin and arrange the pretzels on top. Bake for 25–30 minutes or until the edges are cooked when tested with a skewer and the centre is just set. Allow to cool to room temperature in the tin. Refrigerate for 3 hours or until chilled. 
   
4. Remove the cake from the tin and place on a cake stand or plate. Slice to serve. Serves 8–10
   

+ If you’ll be refrigerating this cake for longer than the specified 3 hours, remove it from the fridge 1 hour before serving to allow it to come to room temperature.