1 teaspoon chile sauce with garlic (such as sambal oelek)
1 red bell pepper, seeded and finely julienned
1/3 cup chopped cashew nuts
2 large mangoes, peeled, pitted, and diced (about 2 1/2 cups)
3 tablespoons chopped fresh cilantro leaves, for garnish
To prepare the marinade, place the soy sauce, sherry, sesame oil, rice vinegar, ginger, garlic, salt, and pepper in a mixing bowl, and mix together. Add the beef, combine well, and let sit in the refrigerator for 1 hour, turning occasionally.
To prepare the rice, place the rice, 1 1/2 cups of water, the butter, salt in a saucepan with a tight-fitting lid. Bring to a boil, and reduce the heat to a simmer. Cover and cook for 20 minutes, or until the rice has absorbed all the liquid. (Add a little more water if the rice is not yet tender.) Remove from the heat and let sit for 5 minutes. Fluff with a fork before serving.
Heat the peanut oil in a wok or large sauté pan until lightly smoking. Add the garlic and ginger and sauté over high heat for 1 minute. Lightly drain the beef mixture and add it to the wok. Stir-fry for 4 to 5 minutes, until browned on all sides. Add the chile sauce, red bell pepper, and the cashew and stir-fry for 2 minutes longer. Add the mango and cook for 1 minute longer, stirring gently.
Spoon the rice onto serving plates and top with the beef mixture. Garnish the beef with the cilantro.