For the dough

• 80 g (2¾ oz) high-quality semi-sweet chocolate
• 80 g (2¾ oz) high-quality milk chocolate
• 125 g (4½ oz) butter
• 1 tbsp instant espresso powder
• 4 eggs
• 140 g (5 oz) raw cane sugar (golden granulated sugar)
• 1-2 tsp vanilla sugar
• 120 g (4¼ oz) flour
• 1 pinch salt
• 300 g (10½ oz) frozen blueberries, defrosted

For the frosting

• 150 g (5½ oz) semi-sweet cooking chocolate
• 50 g (1¾ oz) butter

With baking paper, carefully line a rectangular pan (about 20 x 24 cm/8 inches x 9½ inches). Break the two types of chocolate into pieces. Add to a heat-proof bowl together with the butter and melt over a double boiler, stirring occasionally. Set aside to cool.

Preheat the oven to 180°C (350°F/Gas mark 4). Dissolve the instant espresso in 2 tablespoons hot water. Combine the eggs, sugar and vanilla sugar in a mixing bowl and whisk until foamy. Add the espresso, flour and salt and mix to combine, then stir in the cooled, melted chocolate. Gently fold in the blueberries with a spatula.

Spread the batter evenly across the pan and bake in the preheated oven for 30–35 minutes. Use a toothpick to test for doneness! Allow to cool in the pan.

Melt the semi-sweet cooking chocolate and butter in a double boiler, stirring occasionally. Spread the frosting evenly across the brownies. Leave to set and then cut into pieces about 5–6 cm (2¼ inches) in size.