Heat the butter and oil in a large skillet. Add the potato cakes, cook in batches if needed, and Fry over medium heat until undersides are Golden. Turn over and cook the other side in the same way. If the skillet is ovenproof put it straight into the preheated oven. Alternatively, transfer the cakes to a baking sheet. Cook for 5 to 10 minutes, until the cakes are cooked through.
Meanwhile, line the broiler rack with foil and arrange the bacon and tomatoes on top. Tear the leaves from the Rosemary, chopped, and sprinkle over the tomatoes with a little salt and black pepper. Broil until the bacon is almost cooked, then drizzle with maple syrup and continue to cook until Golden.