In a small pot, bring an inch or two of water to a boil.
Place the steak in the freezer for 15 minutes to make it easier to slice very thinly.
Peel the tangerines; scrape off the pith. Squeeze 1/4 cup juice from the fruit; set aside. Boil peels 1 minute; drain and slice. (If using dried peels, soak in warm water until tender; drain and slice. Peel orange; scrape pith from the peel. Boil peel 1 minute; drain, slice and add to soaked peels. Squeeze 1/4 cup juice from the fruit.)
In a bowl, whisk the tangerine juice, 2 tbsp. soy sauce, 1 tbsp. sherry and the cornstarch. Slice the steak thinly against the grain; mix with the marinade and chill 15 to 20 minutes.
In a large nonstick skillet, heat 1 tbsp. of the stir-fry oil over high. When it ripples and begins to smoke, add half of the beef; stir-fry until browned, 2 to 3 minutes. Transfer to a plate. Repeat with 1 tbsp. oil and the remaining beef. Heat the remaining 1 tbsp. oil in the skillet. Add the shiitakes, scallion whites, chile, ginger, garlic, peppercorns (if using) and snap peas; stir-fry 3 minutes. Add the tangerine peels; stir-fry 1 minute. Add the remaining 3 tbsp. sherry and 2 tbsp. soy, the black bean and hoisin sauces, the brown sugar and sesame oil. Cook until heated through, 1 minute. Add the beef and scallion tops. Stir 1 minute; remove from heat. Serve with the rice. Top with the almonds, scallions and sesame seeds.
