Preheat oven to 175 °C.
Beat the butter and both types of sugar until fluffy. Add one egg at a time while continuing to beat the mixture.
Melt the chocolate over a pan of hot water and set aside to cool.
Chop the pumpkin and mix into the butter mixture. Fold in the melted chocolate.
Mix flour, baking powder and cinnamon together and fold into the mixture.
Grease a sponge cake tin and pour the mixture into it. Use a spatula to smooth the surface.
Bake in the lower section of the oven for about 45 minutes. Remove from the oven and leave to cool for about 10 minutes. Turn the cake out onto a rack and leave to cool again. Cover with a tea towel.
Make the glaze by mixing the icing sugar and freshly squeezed orange juice. Wait for the cake to cool completely before decorating.
The recipe was made by