Add the mirin, sugar and sake to a small pan and stir over a medium heat.
¼ cup mirin, 2 ½ tbsp sugar, 1 ½ tbsp sake
Add the soy sauce and bring to a boil stirring constantly.
¼ cup soy sauce
Immediately reduce the temperature until the mixture in simmering gently. Leave to simmer for 10 minutes. You need the flavours to intensify so the mixture needs to reduce by 1/3rd.
When bubbles start forming around the edge of the pan, the sauce should have reduced by about a 1/3rd. Remove from the heat.
If the sauce continues to thicken, add a little water and heat to whisk in until you achieve the consistency you require.
Line a baking sheet with tin/aluminium foil and gently spray with cooking oil.
Cut the eel into manageable sizes for the serving bowl and place it skin side down.
4 large eel fillets
Preheat the grill to a medium heat, about 260C/500F and move the grill shelf to about 6 inches away from the grill.
Once the temperature has been reached place the baking tray into the grill and cook for about 5 - 6 minutes. The eel will start to blister a little showing its cooked.
Once cooked, remove from the grill and brush a little of the sauce over the eel.
Return to the grill and cook for a further 1 minute.
Serve on a bed of rice that has been brushed with more of the sauce. It all adds layers of flavour and textures.