Heat peanut oil in a wok or large frypan over high heat. Stir in garlic and cook for a few seconds until it begins to brown. Add the capsicum and broccoli then cook until the capsicum begins to brown and soften; about 5 minutes.
Stir together the chicken stock, soy sauce, sherry and cornflour until dissolved. Pour the sauce into the wok and bring to a boil.
Stir in the tofu and cook until hot, about 1 minute. Garnish with cashew pieces to serve.