Heat peanut oil in a wok or large skillet over high heat. Stir in garlic and cook for a few seconds until it begins to brown. Add the bell pepper and broccoli; cook until the pepper begins to brown and soften, about 5 minutes.
Stir together the chicken broth, soy sauce, sherry, and cornstarch 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.