Melt the chocolate and butter in a medium saucepan over a gentle heat. Once melted, add the sugar and stir to combine. Stir in the ground almonds and then leave to cool.
In a separate bowl, beat the eggs until fluffy. Gently fold the eggs into the cooled chocolate mixture, then add the walnuts and pour into the cake pan.
Pour 250 ml water into the multi-cooker. Put the trivet into the pot, then place and set Manual or High Pressure for 12 minutes. At the end of cooking, use the QPR method.
Remove the cake pan and trivet from the pot and leave the cake to cool a little. If necessary, remove any drips of water on the surface of the cake with paper towels.
Cut into triangles and serve.