Put the potatoes and garlic cloves in a saucepan and cover with cold water. Salt the water and bring to a boil; cook until the potatoes are beginning to fall apart when pierced with a fork, about 10 minutes. Drain the potatoes and put them back into the hot pan. Shake the pan and let the potatoes cool to room temperature; transfer them to a mixing bowl.
Add the mustard to the potatoes, and mash with a spoon or potato masher until smooth. In a small bowl, mix the flour, parmesan, ginger, and a healthy pinch of salt and pepper together and sprinkle it over the potatoes. Mix the potatoes very well; taste and add more salt and pepper if necessary.
Put the bread crumbs on a shallow plate and mix in a few tablespoons of flour. Using a large ice cream scoop or two large soup spoons, make a ball of potato mixture and tuck 2 pieces of mozzarella into the center, enclosing them in potato. Gently drop the potato ball into the breadcrumbs and use a fork to push it around and coat completely in crumbs. Youll now be able to pick it up and form it into a patty, about - inch thick. The potato mixture is very soft and tricky to work with, but just be gentle and patient. Just make sure the mozzarella is completely enclosed in potato. Continue making patties you should get 8, although these can be made any size you like.
Heat the oil in a large non-stick skillet over medium heat. Working in batches, if necessary, gently lower the potato cakes into the skillet and cook, turning once, until golden brown and crisp on both sides, about 10 minutes total.
Serve immediately or keep warm in a 200 degree oven until dinnertime. You can sprinkle a little parmesan cheese on top and reheat them also.