Steps

1. Peel and finely grate the ginger in a bowl. To extract its juice (the most potent part of the root), squeeze the grated parts in your hand. You should end up with the stringly bits in your hand, and the juice in the bowl.Discard the stringly bits.
2. Mix the ginger juice with the sake and the soy sauce.Add the pork slices one by one and marinade somewhere chilled for about 30 minutes.
3. Heat up a frying pan(preferably a cast iron one). When hot,pour in half od the oil.Add half of the pork slices, without the marinade, making sure each slice is in contact with the pan. Turn with a spatula and fry both sides at a high heat. Then place to the side.
4. Repeat step 3 with the leftover oil and pork.
5. When cooked, add the first batch of pork back to the pan,and,keeping a high temperature, pour in the marinade sauce and let it quickly reduce, then season to taste.Slice the gari into strips and sprinkle over and serve with rice.

Tip: Ready sliced pork loin can be found in most Japanese shops, but any of good quality will do. For effective slicing, freeze the piece of meat slightly beforehand.