In a small bowl, cover the tapioca with cold water and let soak for 1 hour. Drain the tapioca in a fine sieve.
Bring a medium saucepan of water to a boil. Add the tapioca and cook until it turns clear, about 4 minutes. Drain immediately and return the tapioca to the saucepan. Add the remaining ingredients and bring to a simmer over moderate heat. Transfer the sauce to a bowl and let cool to room temperature, then refrigerate until chilled. Serve cold.