Cook rice to packet instructions adding the soya beans for the final 3 mins.
Meanwhile, mix together the Teriyaki sauce, crushed garlic, lemon zest and juice. Heat a non stick pan over a medium heat. Brush a little Teriyaki sauce over the mackerel and place skin side down for 1-2 mins to sear.
Turn the fish over and pour the Teriyaki sauce mixture into the pan. Bring to a bubble and cook for another 1-2 mins. The fish will warm through and the sauce will thicken.
Spoon cooked rice into bowls. Lay a fillet on top and pour over sauce. Sprinkle with spring onions with Wasabi paste, if you like.