Preheat the oven to 180?. Line the muffins tins with cases or a loaf tin with greaseproof paper.
Peel and grate the carrots.
Using a hand whisk, whisk together the sugar, eggs and oil. Add in the vanilla . Grate in the zest of the orange.
Stir in the carrots.
Sieve in the flour, salt and spices if using.
Fold all the ingredients. Spoon in to the tin / muffin cases .
Bake for 30 minutes. Cool on a wire tray.
Icing : Beat the butter and cream cheese together. Squeeze in the juice of the orange if using. Gradually whisk in the icing sugar and combine until it forms a smooth, rich paste. Stir in the melted white chocolate.
Pipe or spread the icing on top of the cooled muffins. Garnish with some chopped hazelnuts, some grated white chocolate of even some orange zest.