Preheat the oven to 180°C (160°C fan). Line a cupcake tray with cupcake cases and set aside.
Brew 1 Tick Tock Original Rooibos teabag in 60ml of boiling water for 3 minutes. Then remove the teabag and set the tea aside.
For the vanilla batter; in a bowl, whisk the milk and sour cream together and set aside.
For the red velvet batter; in another bowl, whisk the milk, sour cream and Rooibos tea together. Add the cocoa and red food colouring and set aside.
In a separate bowl, mix together the flour, cornflour, baking powder, bicarbonate of soda and salt. Beat in the butter, sugar, eggs and vanilla extract until light and fluffy. Split this mixture equally between the vanilla batter and red velvet batter.
To create a marble effect add 1 tbsp of vanilla batter to each cupcake case, then 1 tbsp of red velvet batter, followed by another tbsp of vanilla batter until the cases are ⅔ - ¾ full.
Bake in the oven for 18-20 minutes, or until a toothpick inserted in the centre comes out clean. Let the cupcakes cool in the tray for 5-10 minutes before moving them to a cooling rack.
For the frosting, use an electric mixer to beat the cream cheese and butter. Gradually add the icing sugar, salt and vanilla extract and mix until light and fluffy.
Put half of the frosting into another mixing bowl. Mix in the cocoa powder and red food colouring. Now you have have your vanilla frosting and red velvet frosting,
Add half the vanilla frosting into a piping bag, carefully pushing it to one side and then add half the red velvet frosting into the remaining side. Ice the cupcakes as desired, adding the remaining frosting to the bag when needed.