Crack the eggs into a bowl then add in mirin, shoyu and sugar. Whisk until mixture is light and fluffy.
Preheat a tamago pan and oil it using a paper napkin.
Pour 1 ladle of the egg mixture into the pan. Once slightly cooked, fold egg to one end.
Repeat folding and adding of egg mixture several times, compressing each layer to form a nice and firmed rectangle shape.
Once completed, set aside to cool before cutting into thick slices.
Slice the sweet potato and set aside.
Peel the prawns and lightly beat to flatten them.
In a bowl, mix the tempura flour and icy cold water to form a batter.
Preheat the oil over high heat for about 3 minutes for it to be hot enough to fry the ingredients. With Rinnai’s RB-2CGT Gas Hob, you can use the auto-timer to preheat the oil.
While waiting for the oil to heat up, coat the sliced sweet potatoes and prawns in tempura flour.
Once the oil is heated, deep-fry the sweet potatoes over medium heat until golden brown. Remove the sweet potatoes from the wok and set on a wire rack over the wok or a paper towel on a plate to cool down and strain off excess oil.
Coat the prawns in the tempura batter (tempura flour + water) and lightly fry for 5 seconds. Remove the prawns and dip into the batter again before continuing to deep-fry until golden brown. When cooked, place on a wire rack or paper towel to remove excess oil. This double frying method will ensure you have a crispy and fluffy prawn.
Preheat a pan and season the salmon fillet with salt.
Sear the salmon for 3 minutes on each side over medium heat.
Then brush the teriyaki sauce over the salmon and allow to continue cooking for 30 seconds on each side.
Once done, remove the salmon from the pan.
Plate up your bento box with the salmon, sliced tamago, tempura ingredients and some rice to enjoy a lovely Japanese bento box meal!