1 1/4 cups water
1 1/4 cups sugar
1 Tbsp instant coffee
1/3 cup cocoa
1 tsp bicarbonate of soda
3 eggs, lightly beaten
1 tsp vanilla extract
1 cup self-raising flour, sifted
1 packet large white marshmallows
Softly whipped cream, optional
Preheat oven to 180C. Line a deep, 18cm square tin with baking paper. Put water, sugar and butter in a large heavy-based saucepan over a medium-low heat. Stir until butter has melted. Add coffee and stir until dissolved and mixture is smooth.
Sift cocoa and bicarb into butter mixture, then whisk until combined. Bring mixture to a gentle simmer and simmer for 5 minute. Stand to cool slightly. Add eggs, vanilla and flour and beat until smooth.
Put cake mixture in the prepared tin. Bake cake for 1 - 1 1/4 hours or until a skewer inserted in the centre comes out clean. Remove cake from oven, and allow to cool in the tin on a wire rack for 30 minutes.
Preheat grill to high. Arrange marshmallows on top of cake, then put cake under grill until marshmallows are slightly melted and golden on top. Remove cake from tin, using baking paper to assist you, and stand on a wire rack to cool. Serve with softly whipped cream, if desired.