Dark Chocolate Walnut Brownies
Coarsely chop the dark chocolate and melt with the butter in a double boiler or heatproof bowl over a saucepan of simmering water. Remove from heat and allow to cool.
Beat the eggs, sugar and bourbon-vanilla sugar with an electric mixer on high speed for 8-10 minutes. Stir the cooled chocolate mixture into the egg mixture, then sift in the flour, baking powder and salt and mix until smooth. Fold in the chopped walnuts.
Line a 41 x 26 cm (approximately 16 x 10 inches) baking dish with parchment paper and spread the batter into the dish. Bake in an oven preheated to 180°C/160°C convection/gas mark 2-3 (approximately 350°F/325°F convection) for 40-45 minutes, until a toothpick inserted comes out clean. Remove from the oven, cool on a wire rack, cut into squares and serve.