Reduced Sugar Carrot Cake

Name: Reduced Sugar Carrot Cake
Ingredients: 200ml (7fl oz) vegetable oil; 3 free-range eggs; 175ml (6fl oz) agave syrup (also known as agave nectar); 400g (14oz) carrots, peeled and grated; 275g (9¾oz) self-raising flour; 2 tsp baking powder; 1 tsp ground cinnamon; 1 tsp mixed spice; 150g (5½oz) sultanas; 150g (5½oz) walnuts pieces; 1 orange, finely grated zest only; 400g (14oz) full-fat cream cheese; 50g (1¾oz) unsalted butter, softened; 50ml (2fl oz) maple syrup; 25g (1oz) walnut pieces, chopped; ground cinnamon, for dusting