In the bowl of a stand mixer, whisk flours, sugar and yeast together.
Add margarine, milk, egg and Marmite. Using a dough hook attachment, mix on a low speed until combined.
Increase to high speed and knead until a smooth dough forms.
Transfer to a greased bowl. Cover and place in a warm place until doubled in size, about 1 hour.
Once doubled in size, punch the air out of the dough and divide into 15 portions. Roll each portion into balls and place evenly spaced apart on a greased baking tray. Cover and set aside in a warm place until doubled in size, about 1 hour.
Preheat oven to 180°C.
To make the crosses, place the Marmite in a piping bag. Pipe Marmite across the hot cross buns to make crosses.
Bake for 20-25 minutes or until browned and cooked through.