1. Preheat your oven to 160°C and line a brownie tin with baking paper.
  2. Beat the butter, cocoa and sugar together in a stand mixer until light and fluffy and the mixture is no longer grainy. Be careful though – the cocoa likes to ‘poof’ when you turn the mixer on so best to cover with a tea towel!)
  3. Add the eggs one at a time, beating well after each addition.
  4. Fold through the flour, walnuts and white chocolate.
  5. Pour evenly into the lined tin and smooth the top.
  6. Swirl the boysenberry jelly through the brownie batter. This will go nice and sticky when it cooks.
  7. Cook for 50 minutes or until a knife comes out clean when inserted.
  8. Serve with mascarpone and the boysenberry ‘coulis’.