Photographs: Karen Thomas
Preheat the oven to 180°C, fan 160°C, gas 4. Grease 2 x 20cm sandwich tins and line the bases with baking paper.
Bake the nuts for 8-10 minutes. Tip the flour, baking powder and cinnamon into a food mixer. Mix in the eggs, sugar, oil and vanilla. Stir in the squash and chocolate. Chop the nuts and add 100g.
Divide the mixture between the tins and bake for 35-40 minutes. Cool for a few minutes, then turn on to a wire rack and leave until cold.
For the icing, break the chocolate into pieces in a bowl. Heat the cream and sugar, stirring, until just below simmering point. Pour the cream on to the chocolate; stir to melt. Cool, then chill the icing for 20 minutes.
Sandwich the cake with the icing; spread the rest on the top and sides. Sprinkle with the remaining nuts.