Got the recipe from babe in the city blog. Tried it few times and it is easy and nice 
Mississippi Mud Cake
Serving size: Serves 10 or more
Cooking time: More than 1 hour
Can be made 3 days ahead. Storage: Covered, in refrigerator. Freeze: Suitable. Microwave: Chocolate mixture suitable.
INGREDIENTS
250g cold unsalted butter, chopped
150g dark chocolate, chopped
440g (2 cups) caster sugar
250ml (1 cup) hot water
80ml (1/3 cup) whisky
1 tablespoon instant coffee powder
225g (1½ cups) plain flour
35g (¼ cup) self-raising flour
25g (¼ cup) cocoa powder
2 eggs, lightly beaten
METHOD
Grease 23cm square slab pan, line base with baking paper. Combine butter, chocolate, sugar, water, whisky and coffee powder in medium pan; stir over low heat until chocolate is melted. Transfer mixture to large bowl; cool. Stir in sifted flours and cocoa, then eggs; pour mixture into prepared pan.
Bake at 160°C for 1¼ hours. Stand cake 30 minutes; turn onto wire rack to cool. Serve dusted with sifted icing sugar.
Ref: The Australian Women ‘s Weekly – Food We Love. Original recipe can be found here.
