Butter, for greasing
200g good quality dark chocolate (70% cocoa)
200g icing sugar
3 eggs, at room temperature
40g flour, sifted
Preheat the oven to 170C/325F/Gas mark 3. Grease a 20 x 20cm baking tin and line it with baking parchment, leaving a little overhanging on every side.
Break the chocolate into pieces and melt it in a heatproof bowl set over a pan of barely simmering water. Once the chocolate has melted, remove from the heat and beat in 40ml of lukewarm water, followed by the icing sugar. Add the eggs one by one, stirring vigorously to ensure a smooth consistency. Stir in the flour.
Pour the batter into the prepared tin and bake in the oven for 20-25 minutes, or until small cracks appear on the surface. Serve warm with ice cream, or cold alone.