Tip the rice into a bowl. Cover with cold water and whisk for 1-2 mins (you can use a fork) till the water goes cloudy (this is the starch). Drain, rinse the rice under cold water. Tip back into the bowl. Cover with fresh water. Set aside.
Tip the peanuts into a wok or deep frying pan. Toast over a medium heat for 2-3 mins till the peanuts smell nutty and are golden brown. Tip into a tea towel and rub to remove the skins. Set aside.
Separate the pak choi leaves. Finely shred the thick stems and keep them separate from the leaves. Shred any large leaves. Trim the roots and dry tips off the spring onions. Finely slice them. Put the sliced white parts of with the pak choi stems and the green parts with the pak choi leaves.
Drain the rice and tip into a small pan. Add 400 ml boiling water and a pinch of salt. Cover. Bring to the boil, then turn the heat down and simmer for 8 mins till all the water is absorbed and the rice is tender. Take off the heat. Set aside, lid on, for 4 mins to finish cooking the rice.
While the rice cooks, tip the chicken into a bowl and add 1 tbsp cornflour. Season. Toss to coat the chicken in the flour. Warm the wok over a high heat for 1-2 mins. Add 1 tbsp oil and the chicken (shake off any excess cornflour and keep in the bowl for later). Stir fry for 5-8 mins till golden all over.
Add the Szechuan peppercorns and ½-1 tsp chilli flakes (or more if you like – they're spicy). Add the pak choi stems and the white parts of the spring onions. Stir fry for 2 mins.
Tip in any leftover cornflour. Crumble in the chicken stock cube. Pour in 2 tbsp each rice vinegar and tamari. Add 200ml boiling water. Bubble up, then turn the heat down and simmer for 4-5 mins to cook the chicken through.
Add the peanuts and pak choi leaves to the wok. Toss to mix and wilt the leaves. Divide the rice between 2 warm bowls. Top with the gong bao chicken and garnish with the green spring onion tops to serve.