Wash 300 g filleted eels with cold running water. Cover a chopping board with a sheet of plastic wrap and place the eel on top. Cut each eel into 2-3 pieces by pressing a sharp knife into the area you want to cut, and pushing the eel back and forth over the plastic wrap.
Place the eel in a cold frying pan with the skin side down and add 2 tbsp sake.
Turn on the heat on medium and steam for 5 minutes with the lid on. While it's steaming, preheat the grill/broiler on medium-high for 5 minutes.
After 5 minutes, remove the pan from the heat and transfer the eel skin side down to a wire rack lined with aluminum foil. Grill for 6 minutes.
Turn the eel over and grill the skin side for 5 minutes.
Apply the sauce generously but evenly over the skin and grill for 30 seconds.
Turn the eel over and apply the sauce on the meat side and grill for 30 seconds. Repeat brushing and grilling each side twice more (3 times in total).
Dish up 2 portions cooked Japanese short-grain rice and brush the top with the leftover sauce.
Place the eel on top and sprinkle with ground Japanese pepper (sansho).
Enjoy!