In a medium bowl combine the mirin, soy sauce, sugar, ginger, sesame oil and cornstarch. Whisk well.
Cut the chicken thighs into bite size pieces and mix them into your sauce to marinate while you prepare the rice.
Cook your rice according to package directions and along with the water add in the salt, sesame oil and sesame seeds.
While the rice cooks, heat a large, heavy skillet (I use a 12β cast iron) over medium high heat and add in the oil. When itβs hot, remove the chicken from the sauce, allowing excess to drip back into the bowl and carefully place the chicken in a single layer in your pan. Let it cook, undisturbed for 2-3 minutes so the bottom caramelizes.
Give the chicken a stir. Let it caramelize for 2-3 more minutes then pour in the reserved sauce.
Let the chicken bubble and simmer in the sauce for another 2-3 minutes until slightly thickened and the chicken is cooked through.
Pile the rice into serving bowls and top with the chicken, pineapple and cucumbers. Add extra sauce, as desired and top with sliced scallions.