You will need 2 x 8 inch cake tins.
Preheat oven to 180C (160C with fan) Gas mark 4.
Sieve the flour and bicarbonate of soda together in a large bowl. Place the 125g of dark chocolate in a microwave safe bowl and microwave for 30 seconds or until melted. Add the oil, water, Carnation Condensed Milk, eggs and vanilla to the melted chocolate and stir till smooth.
Make a well in the middle of the flour and then pour in half the chocolate mix. Stir well then add the other half and mix till smooth.
Pour the mixture into 2 prepared 8 inch cake tins and bake for 25 minutes or until a skewer to the centre comes out clean. Cool completely.
Whilst the cake is baking, make the truffles. Place the cream and dark chocolate in a microwave safe bowl. Heat on high for 1 minute or until the cream is hot and the chocolate beginning to melt. Whisk together until smooth and glossy, then refrigerate until firm.
Sieve the cocoa into a large bowl, roll the chocolate mix into 16 balls then toss in the cocoa powder to cover.
Sandwich the cakes together with the Carnation Chocolate filling and topping then use the remainder to cover. Decorate with the truffles.
Recipe courtesy of Carnation®