2/3 Cup extra virgin olive oil
1/2 Tablespoon balsamic vinegar
1/4 Teaspoon grated orange peel
1/4 Teaspoon grated lemon peel
1/4 Teaspoon Worcestershire sauce
Combine all ingredients except for the oil in a glass or stainless steel bowl. Whisk well. Allow mixture to rest for 15 minutes. Slowly whisk in oil, pouring it in a steady stream and whisking continuously to make an emulsion.
Cover and chill for 1 hour before serving.