Rinse the rice until the water runs clear. Put in a small saucepan with 250ml (1 cup) water, cover and bring to a simmer over medium heat. Reduce the heat to low and cook for 12 mins or until tender and the water is absorbed. Turn off the heat and stand, covered, for at least 5 mins.
Step 2 — Pickle cucumber
Meanwhile, thinly slice the cucumber on an angle. Combine 3 tsp white vinegar and 1 tsp sugar in a bowl. Add the cucumber and toss to coat. Set aside to pickle, tossing occasionally, until needed.
Step 3 — Prep ingredients
Thinly slice the onion. Trim the beans and halve on an angle. Cut the chicken into 2cm chunks. For the sauce, combine the cornflour and pho seasoning in a bowl. Add the stir-fry sauce, 1 tsp soy sauce, ½ tsp sugar and 180ml (¾ cup) water and whisk until combined.
Step 4 — Cook chicken
Heat 2 tsp oil in a medium deep frypan over high heat. Cook the chicken, stirring occasionally, for 5-6 mins until almost cooked through. Remove from the pan.
Step 5 — Cook vegetables and sauce
Heat 2 tsp oil in the same pan over medium-high heat. Cook the onion and beans, stirring, for 4-5 mins until softened. Return the chicken and any resting juices to the pan and cook, stirring, for 1 min. Whisk the sauce to combine. Add the sauce to the chicken mixture and bring to a simmer. Cook, stirring, for a further 1 min or until the chicken is cooked through.
Step 6 — Get ready to serve
Pick the mint leaves, discarding the stems. Fluff the rice with a fork. Divide the rice, chicken mixture and pickled cucumber among bowls and drizzle with any remaining pickling liquid in the bowl. Scatter with the mint and a pinch of chilli flakes*, if desired, to serve.