A rather pleasing carrot cake with lime mascarpone icing

INGREDIENTS

• 250 g unsalted butter, softened
• 250 g light brown soft sugar
• 5 large free-range eggs
• zest and juice of 1 orange
• 170 g self-raising flour, sifted
• 1 slightly heaped teaspoon baking powder
• 100 g ground almonds
• 100 g shelled walnuts, chopped, plus a handful for serving
• 1 heaped teaspoon ground cinnamon
• 1 pinch ground cloves
• 1 pinch ground nutmeg
• ½ teaspoon ground ginger
• 250 g carrots, peeled and coarsely grated
• sea salt
• 100 g mascarpone cheese
• 200 g full-fat cream cheese
• 85 g icing sugar, sifted
• zest and juice of 2 limes