Apple & walnut cake with treacle icing

Name: Apple & walnut cake with treacle icing
Prep time: 20 min
Cook time: 45 min
Total time: 1 h 5 min
Cuisine: British
Ingredients: 300g plain flour; 1 tsp ground cinnamon; ½ tsp bicarbonate of soda; 140g dark brown soft sugar; 50g golden caster sugar; 250ml rapeseed or sunflower oil; 4 eggs; 3 unpeeled apples coarsely grated; 100g walnuts roughly chopped; 100g butter softened; 50g dark soft brown sugar; 1 tbsp black treacle; 200g tub full fat soft cheese