Bring a large saucepan 3/4 full of water to a boil. Add the peas, reduce heat and simmer for 2 minutes. Drain the peas then plunge them into a bowl of ice water to stop the cooking. Drain again thoroughly and set aside.
To prepare the sauce, combine the soy sauce, rice vinegar, brown sugar, cornstarch and five-spice powder in a small bowl. Stir until the cornstarch and seasonings have dissolved. In a large skillet, heat the sesame oil over medium heat. Stir in the garlic and peas. Increase the heat to high, stirring frequently. Pour in the soy sauce mixture and cook until thickened, 1 to 2 minutes. Sprinkle with crushed red pepper, if desired. Serve immediately.