The basic components of this dressing can be varied to suit your tastes. Try, for example, red wine, balsamic, or rice vinegar instead of white wine vinegar; use vegetable or chicken broth in place of water; substitute other fresh herbs for the oregano, such as chives, tarragon, or basil.
Combine water and cornstarch in a small saucepan, stirring with a whisk until cornstarch dissolves. Bring to a boil over medium-high heat; cook 1 minute, stirring constantly. Remove from heat; cool. Stir in vinegar and remaining ingredients. Cover and chill.