Instructions

1. Half-melt the butter and chocolate over a low temperature. Turn off the heat and allow to melt completely. Let it cool.
2. Preheat the oven to 180°C.
3. Grease a 25 × 30 cm baking tray and line with parchment paper.
4. In a mixing bowl, lightly beat the eggs, then add the sugar and beat until creamy. Stir in the grated orange zest and walnuts. Fold in the butter-chocolate mixture then sift in the flour. Mix gently (do not over-stir!)
5. Transfer the batter into the baking tray, spread it out evenly.
6. Bake for about 25 minutes, until jut cooked through (the middle should remain a little s sticky).
7. Let it cool in the tin, then cut into cubes.
8. Dust with icing sugar before serving, if you like.