Slice mushrooms and onions. Drain pimento. Add enough water to broth to make 2 1/2 cups. Bring to a boil in a medium saucepan. Stir in rice. Cover tightly and simmer for 20 minutes. Remove from heat and let stand, covered, until all liquid is absorbed; about 5 minutes. Transfer rice to large bowl. Combine oil, soy sauce, salt and sesame seeds (optional); mix well. Stir into hot, cooked rice. Cover and chill. Stir in remaining ingredients before serving.