Preheat the oven to 180°C fan and place 12 paper cases in your muffin tray. Sift all the dry ingredients together; flour, salt, baking powder, cinnamon ground ginger & nutmeg. Set aside. 

In the bowl of your KA stand mixer, whisk the eggs and brown sugar until fluffy and pale, about 4-5 minutes. Add the oil, gradually and combine. 

Slowly incorporate the dry ingredients into the bowl and mix until combined. 

Remove bowl from machine and add the carrots and then the chopped walnuts. 

Pour into the cases (2/3 of the height) and bake for about 20- 25 minutes. Check they are done by inserting a toothpick or small knife inside the cupcake, it should come out clean.   

While baking, prepare the frosting: 

In the KA bowl, beat the butter and icing sugar with the paddle attachment until light and fluffy, about 5-6 minutes. Drain the mascarpone from any liquid, and soften with a spatula. Now add, gradually, to the buttercream, making sure every bit is incorporated before adding any more. 

When the cupcakes are ready and cold, frost generously with the mascarpone cream and serve. Storage: if not frosted, the cupcakes will keep at room temperature for up to 4-5 days; if frosted, they will keep in the fridge, better in an airtight container, for 2-3 days.