1. Preheat oven to 170C. Grease and baking paper line 3 x 20cm cake tins.
2. Place butter and caster sugar in the bowl of an electric mixer fitted with a balloon whisk and whip until pale and creamy.
3. Beat in eggs and vanilla.
4. Add the flour, milk and oil and beat at a low speed until combined. Increase speed to high and beat for 60 seconds. Fold though 200g of Caramilk Baking chips.
5. Divide evenly between the prepared tins (mine each weighed approx. 500g) and bake for 30-35 minutes or until a skewer inserted comes out clean. Leave to cool for 5 minutes before turning onto a wire rack to cool completely.
6. For the buttercream, place butter into the bowl of an electric mixer and beat until very pale.
7. Add the vanilla paste and icing sugar and beat at a low speed until combined then increase the speed and beat until fluffy, adding a little milk if required.
8. For the chocolate drizzle, melt the dark chocolate with the oil in a small microwave safe bowl, in a microwave in 30 second bursts until melted. Stir to combine and leave to cool.
9. To assemble, lace 2/3rds of the icing into a piping bag fitted with a round nozzle. Place one cake on a serving plate and pipe a 1cm layer of icing on top, taking it to the edges. Place the second cake on top, ensuring that it is level. Pipe a 1cm thick layer of icing on top, taking it to the edges and place the last cake on top. Ensure all your cakes are level and sitting directly on top of each other. Pipe the remaining icing over the sides and top of the cake and smooth with a flat bladed spatula. Spoon the remaining butter cream on the top of the cake, piling it nice and high, and swirl with the back of a spoon.
10. Drizzle with dark chocolate and decorate with remaining 60g of CARAMILK Baking Chips.