Steam the pumpkin, peeled and cubed, for 20 minutes.
Preheat the oven to 180°C. Whisk the eggs in a bowl. Pour in the maple syrup, sifted flour, melted butter, and sunflower oil. Mix well to obtain a homogeneous texture without lumps.
Pour half of this dough into a second bowl. Mix the pumpkin finely and then mix the purée obtained with the paste of the first bowl.
Melt the chocolate in a double boiler and mix it with the second bowl. Pour successive layers of pumpkin and chocolate into a non-stick cake tin, then place in the oven halfway up and bake for 50 minutes.
Remove from the oven and allow to cool to room temperature. Unmould and serve the cake with a chocolate sauce.