Peel and coarsely grate the potatoes and parsnips - if you're using a food processor, attach the medium grater.
Squeeze out as much liquid as possible with your hands and put them in a bowl.
Stir in the onion, garlic, egg and season if you like. Divide the mixture into six and roughly shape into flat cakes.
Heat 2 tbsp of the oil in a large non-stick frying pan and fry three of the cakes on a low heat for 4-5 minutes on each side until golden and tender. Transfer to kitchen paper with a slotted spoon and leave to cool while frying the remainder adding remaining oil as necessary. Meanwhile grill the bacon and tomatoes, poach the eggs and serve alongside.