Melt the miso paste and butter in a lidded wok or frying pan over a medium heat for a minute and whisk together. Add the chilli flakes, mushrooms and sesame seeds and stir-fry for 3–4 minutes.
Add the mangetout and asparagus to the wok with 1 tablespoon water. Cover and steam for 1–2 minutes, then uncover.
Add the teriyaki sauce and soy sauce and stir-fry for 2–3 minutes. Add the cooked rice and cook for 1–2 minutes more to heat through.
Remove from the heat and serve, scattered with the spring onions and the rest of the sesame seeds.
You could easily add fish or chicken to this dish.