Start this recipe by grinding together the chilli flakes and peppercorns in a pestle and mortar to a fine powder and put aside. Heat the oil in a wok till smoking, then add the garlic, ginger and onion and stir fry for 1-2 minutes. Add the chilli and peppercorn mixture and stir fry for a further minute. Next, add the tofu pieces and broccoli to the pan and stir fry until pale golden-brown on all sides. Meanwhile in a small bowl, whisk together the soy sauce, sherry, rice wine vinegar, caster sugar and half of the water until well combined. Add the mixture to the wok and stir to coat the vegetables and tofu in the mixture. Bring the mixture to a simmer and continue to cook for 2-3 minutes, or until the broccoli is tender. Mix the corn flour with the remaining water and stir into the pan. Toss the stir-fry around in the pan until the sauces have thickened. Sprinkle in the cashew nuts and serve immediately with boiled jasmine rice.