Wash 300 g filleted eels with cold running water. Cover a chopping board with 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 frying pan with the skin side down and add 2 tbsp sake.
Turn on the heat to medium and steam for 5 minutes with the lid on. Remove it from the heat and line the grill with foil. Preheat the grill on medium-high for 5 minutes.
Place the eel on the foil with the skin side down and 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 2 more times on each side.
Cut the grilled eel into strips.
Mix some of the left over unagi sauce with the rice. (Approx 1/2 tbsp per 2 portions of rice.)
Divide the rice into wooden bowls and top with the grilled eel. Brush liberally with more unagi sauce.