Combine the cake mix with all the other ingredients up to and including the butter, beat until smooth for approx. 3 mins. using the whisk on a hand mixer.
To colour the cake mixture
Divide the mixture into four bowls. Add several drops of food colouring (in increasing amounts) to three of the bowls, mix well. Transfer the first two cake mixtures to the two springform pans, cover and chill the other two bowls.
Bake for approx. 15 mins. in the centre of an oven preheated to 180°C. Remove from the oven, allow to cool slightly, remove from the tin, leave to cool on a cooling rack. Repeat the process for the remaining two cake mixtures.
Beat the mascarpone until smooth, stir in the quark, icing sugar and vanilla paste. Refrigerate for approx. 30 mins.
To assemble the cake
Spread 1/3 of the mascarpone mixture over the darkest sponge, then alternate layers of sponge and mascarpone mixture to create a graduated colour effect, finishing with the plain sponge on top. Spread the remaining mixture all over the cake.
Allow to cool for min. 1 hr. Decorate the cake all over with hundreds & thousands before serving.