- Chop onion and set aside.
- Heat up 2 tbsp oil in a frying pan. Add chopped onion and cook, continuous stirring until softened but do not change color. Add mashed potatoes, cabbage, season with salt and plenty of pepper, mix all together in a small bowl.
- Now add vegetables to the pan; stir well and press the mixture with large spoon into a large even cake. Cook gradually on medium heat for maximum 15 minutes.
- When you see the cake has browned underneath, flip the cake pan onto a large plate. Shake gently to release the cake. Add remaining oil to the pan, when hot then slip the cake to the pan, the cooked (browned) side should be uppermost.
- Cook Bubble Squeak over medium flame for at least 10 minutes or so, until the bottom side is golden brown, then cut into wedges and you may serve it hot.