Mrs. Tanaka used to make the best after school snack for her granddaughter, and my daughters would come home raving about the tuna and potato dish.  I have recreated it here:

Skin and cut raw potatoes into little logs.  Soak in slightly salted water, drain well, pat dry.

Open a can or 2 of tuna – I like the Coral brand in oil – but any brand will do.

Put a tablespoon of vegetable oil (or use the oil from the can of tuna) in a pan and stir fry the potato logs until almost cooked.  At this point you can add ginger, garlic, or whatever you want.  I usually keep it simple and don’t add anything.

Drain and add the tuna meat from the can.  Add mirin or brown sugar (about 1 TBS or more) and soy sauce (about 2 TBS or more).  Optional:  add a tsp of hon dashi or saimin base powdered seasoning.

Using a wooden spatula, mix from the bottom gently, let simmer for a few minutes.

Serve with hot rice and enjoy!