Makes 24 squares
275g/10oz/1¼ cups butter, softened, plus extra to grease
275g/10oz/1¼ cups caster (superfine) sugar
5 medium (US large) eggs
275g/10oz/2¾ cups self-raising (self-rising) flour
125g/4oz/1 cup ground almonds
1 tsp baking powder
grated zest of 1 orange
juice of 2 oranges
6 tbsp milk
225g/8oz/2 cups blueberries
4 tbsp hazelnuts
150g/5oz/scant 1 cup icing (confectioner’s) sugar
1 Preheat the oven to 190°C/375°F/Gas 5. Butter a 30 x 20cm/12 x 8in shallow tin. Line with parchment paper.
2 Beat the butter and caster sugar in a large bowl until fluffy. Beat in the eggs, one at a time. Sift in the flour and baking powder, then add the ground almonds, orange zest, the juice of 1 orange and the milk. Beat until light and fluffy.
3 Fold in the blueberries with a metal spoon, distributing them evenly throughout the mixture. Spoon into the prepared tin and sprinkle with the hazelnuts.
4 Bake for 40–45 minutes until well risen and springy to the touch. Cool in the tin for 5 minutes, then turn out on to a wire rack and set aside to cool.
5 Sift the icing sugar into a bowl, then gradually mix in the remaining orange juice, until smooth and runny. Drizzle over the cold cake and set aside for 30 minutes to set.