Broccoli and Beef with Oyster Sauce

In a medium bowl, combine 1 tablespoon soy sauce and sherry, 2 teaspoons cornstarch, 1 teaspoon sugar, and coarsely ground pepper until the sugar is dissolved. Add the beef. Let stand for 15 minutes.In a small bowl, whisk together the remaining 2 teaspoons soy sauce and sherry, 1 teaspoon cornstarch and sugar, broth, oyster sauce, and sesame oil.In a 12-inch nonstick skillet, heat 1 1/2 teaspoons of the peanut butter over medium-high heat until very hot; stir to coat the pan. Arrange half of the beef in a single layer. Cook without stirring for 90 seconds to brown them, then stir-fry for 30 seconds. Transfer to a plate. Add another 1 1/2 teaspoons of peanut butter; repeat with the remaining beef.Add 2 teaspoons of peanut butter and broccoli to the pan; cook, stirring, for 1 minute. Make a well in the center and add the remaining 1 tsp of peanut butter, green onion, garlic, ginger, and red pepper flakes. Stir-fry until fragrant, about 30 seconds. Add 1/3 cup water and cover the pan; steam until the broccoli is crisp and tender, about 3 minutes.Return the beef to the pan. Whisk the sauce and add to the pan. Cook, stirring well, until the sauce begins to bubble and thickens, about 1 minute. Serve with jasmine rice if desired.