Start this recipe by preparing, greasing and lining 2 x 20cm heart shaped tins with non-stick baking paper. Beat the butter substitute, sugar and vanilla together in a bowl until pale and fluffy. Add the eggs one at a time, beating after each addition (if the mixture looks curdled add a spoonful of the flour.) Mix the yogurt with the food colouring – it should look very, very red since the mixture will fade once cooked. Beat the yogurt into the cake mixture. Fold in the remaining flour and cocoa powder, followed by the milk until well combined. Spoon the mixture into the cake tins and bake for 30-40 minutes, or until well risen and golden-brown and a skewer inserted into the middle comes out clean. When the cakes are ready, remove them from the oven and allow to cool completely. Meanwhile, you can prepare the vanilla frosting. Place the cream cheese, mascarpone cheese and vanilla essence in a bowl and beat together lightly with an electric whisk until smooth. Add in the icing sugar and continue to beat till the mixture is smooth. In another bowl, whip the cream to stiff peaks and gently fold into the cream cheese and yogurt frosting. You should end up with a light, smooth vanilla frosting. To assemble the red velvet cake, cut each cake layer in half horizontally using a sharp knife, giving you 4 cake layers. Place one of the cake layers on a serving plate and spread over some of the vanilla frosting. Place another layer of cake on top and repeat the process with the remaining 2 cake layers. Use the remaining frosting to ice the top. Finally, decorate with fresh strawberries and mint leaves.