Ingredients: (Makes 12 squares)
- 150 g/5½ oz plain chocolate (70% cocoa solids), broken into pieces
- 100 g/3½ oz butter
- 1 teaspoon strong instant coffee
- 1 teaspoon vanilla extract
- 100 g/3½ oz ground almonds
- 175 g/scant 1 cup superfine (caster) sugar
- 4 eggs, separated
Preheat the oven to 180°C/350°F/Gas 4. Grease, then line a 20 cm/8 inch square cake tin with baking parchment. Place the chocolate and butter in a heatproof bowl set over a pan of gently simmering water – make sure the bottom of the bowl does not touch the water. Stir gently, very occasionally, until melted.
Carefully remove the bowl from the heat and stir in the coffee and vanilla extract. Add the almonds and sugar and mix well until combined. Beat the egg yolks lightly then stir them into the chocolate mixture.
Whisk the egg whites until they form stiff peaks. Carefully fold a large spoonful into the chocolate mixture, then fold in the rest until completely mixed in.
Spoon the mixture into the prepared tin and bake for 35-40 minutes until risen and firm on top but still gooey in the center. Leave to cool in the tin, then turn out, remove the baking parchment and cut into 12 pieces.