Preheat oven to 180°C / 360°F and arrange a baking tray onto the middle shelf.
In a large bowl, mix all the wet ingredients.
In another large bowl, mix together the dry ingredients exept for the carrots and nuts.
Gently fold the dry ingredients into the wet ones. Mix until fully combined, being careful not to overwork the mixture.
Finally add chopped carrots and nuts. Butter the cake pan and sprinkle with sugar, pour the mixture in, making sure that it does not exceed ⅔ of the mold.
Bake the carrot cake for about 40 minutes, or until a toothpick inserted in the center comes out clean.
In the meantime, whisk the mascarpone cheese with sugar, until you to get a smooth and rich cream. Add freshly grated orange zest and juice and mix until just combined. Refrigerate until ready to use.
When the cake is ready, remove from the oven and let cool before removing it from the pan.
Cut the cake in half horizontally, and spread the cream on the surface. You can cover the cake entirely with cream or just the top of it.
Decorate with chopped nuts and carrot flakes and serve, or store in the fridge until you're ready to serve.