Heat oven to 180C/160C fan/gas 4 and oil a 12-hole muffin tin, or line it with muffin cases. In a large mixing bowl, mix the sugar, flour, bicarb, mixed spice and orange zest. Whisk together the eggs, oil and yogurt, then stir into the dry ingredients along with the grated carrots. Pour the mixture into the prepared tin, or divide between the cases, if using, then bake for 20-22 mins until a skewer inserted in to the middle comes out clean. Turn the cakes out onto a wire rack and leave them to cool a little.
Meanwhile, to make the syrup, heat the honey and orange juice in a pan. Bring to the boil, then simmer for a minute until syrupy. Spoon a few tsp over each cake while still warm, then leave to cool completely. For the icing, mix the mascarpone, yogurt and icing sugar until just combined (if you over-mix, it will become runny). Use a palette or cutlery knife to swirl the icing on top of the cakes, drizzle with a little more honey, if you like, and decorate with edible flowers or orange zest.