I use loin meat from a wild hog here, but obviously store-bought pork is fine, too. Chicken, pheasant, grouse or turkey breast is another good option. I like shiitake mushrooms, but you can use any meaty mushroom, wild or store-bought.
Slice the ginger into pieces that will fit into a garlic press and squeeze out the juices until you get to 2 to 3 tablespoons. Alternately, you can extract the juices with a microplane grater or Japanese ginger grater.
Slice the pork loin against the grain into medallions. Put the medallions between two pieces of plastic wrap, and, using a rubber mallet, meat mallet or empty wine bottle, pound the cutlets to about 1/4 inch thick. Salt them.
Salt the cutlets, then dust them in the rice flour. Set aside.
Heat the oil in a frying pan over medium-high heat and saute the pork loins. Sear for 2 minutes on the first side, then turn and lower the heat to medium and finish cooking to your liking, generally another 2 to 4 minutes. Remove the cutlets and put them in an oven set to "warm."
Add the sake, mirin, soy sauce and ginger juice to the frying pan and bring to a boil. Add the mushrooms and boil furiously for 4 minutes. Turn off the heat.
Take the pork cutlets out and slice them, giving everyone some. Pour the sauce and mushrooms over the pork and serve.