Combine the butter and the muscovado sugar and cream with a hand mixer for a couple of minutes at medium speed.
Always mixing, add the eggs, one at a time. When the eggs are combined, add the roasted pumpkin puree and keep mixing until incorporated. Stop the mixer.
In another bowl, combine all the powders (flour, cocoa, cinnamon, baking powder and baking soda). If using unsalted butter, add 1/4 tsp salto to that.
Add half of the powder mixture to the other bowl and incorporate it mixing at slow speed. Stop the mixer, add the second half of the powders and do the same, until all is incorporated.
Pour the batter into a medium Bundt pan that has been previously greased and bake in the preheated oven at 180°C for 40-45 min. Once baked, let the cake sit in the pan for about 20 minutes before taking it out.
When the cake has cooled down to room temperature, combine the chocolate and cream and set on the stove on a double boiler. When the chocolate has melted, remove from the heat and stir to combine. Pour the ganache over the cake letting it drizzle down the sides.