* Preheat the oven to 180ºC (fan oven)/gas mark 6
* Cream together the butter and sugar until light and fluffy. Add the eggs gradually. Then the food colouring and beat everything until incorporated.
* Sift together the flour and cocoa then add half to the batter. Beat in the buttermilk and finally add the second half of the flour mixture.
* In a ramekin, mix together the bicarbonate of soda and the vinegar, which will fizz as you add them together. Add to your mixture immediately, folding everything in with a spatula.
* Add 1/3 of the batter to the bundt cake tin, then place the vanilla hearts, upside down (remember you'll be turning the cake out, so the point of the heart should be poking up), securely in the batter. Arrange these in a fan shape around the centre point and be careful not to break the vanilla hearts when pushing into the batter.
* Carefully place the remaining red velvet cake batter around the vanilla hearts, taking care not to do not move them.
* Place in the oven, on a medium shelf, and cook for 40 minutes, or until well risen. Once cooked turn out onto a wire rack to cool.
* Whilst the cake is cooling make the cream cheese frosting.