Catherine Berwick's Parsnip & maple syrup cake

INGREDIENTS

• 175g butter , plus extra for greasing
• 250g demerara sugar
• 100ml maple syrup
• 3 large eggs
• 250g self-raising flour
• 2 tsp baking powder
• 2 tsp mixed spice
• 250g parsnips , peeled and grated
• 1 medium eating apple , peeled, cored and grated
• 50g pecans , roughly chopped
• zest and juice 1 small orange
• icing sugar , to serve
• 250g tub mascarpone
• 3-4 tbsp maple syrup