Method

• 1.
  Preapre brownie according to packet instructions and bake in a 20cm x 30cm lamington pan lined with baking paper. Remove from the oven and cool completely, then cut a 19cm round of brownie, discarding offcuts.
• 2.
  Grease a 22cm springform cake pan. Place 100g chocolate and cream in a heatproof bowl set over a saucepan of gently simmering water, stirring until melted and smooth. Remove from heat and cool slightly. Dust savoiardi with cocoa on both sides, then, working with one biscuit at a time, lightly dip one side in the chocolate mixture. Arrange upright around the edge of the prepared pan, pressing the biscuits together to stick. Repeat until pan is lined with savoiardi.

• 3.
  Place brownie in the pan inside the biscuits to create a base, then spread with chocolate chip ice cream. Freeze for 1 hour or until firm, then spread pistachio ice cream over the top and freeze for 4 hours or until frozen. Remove from pan and scatter with remaining 50g chopped chocolate and pistachios to serve.