Delicious squares of crunch and blueberry delight. This cake keeps well if covered at room temperature for 3 days. If longer, it might be best to keep it in the fridge. It gets better each day. Ingredients: Topping: 80g cake flour 200g castor sugar 2 tsp (5.2g) ground cinnamon 110g cold unsalted butter 100g walnuts, chopped Pinch of salt (1/2 tsp / 3.5g) Cake: 480g cake flour 4 tsp (16g) baking powder 1 tsp (7g) table salt 110g unsalted butter, softened 300g castor sugar Zest of 2 lemons 2 large eggs 2 tsp (10ml) vanilla extract 800g frozen blueberries 1 cup (250ml) full cream milk Icing sugar, for dusting (1 tbsp / 7.8g) 0.5g spray and cook