Heat the oil and saute both kinds of onions for 2-3 minutes, stirring, until softened a bit.
Add everything else except the parsley and bring to a boil, then reduce the heat, cover and simmer for 15 minutes. .
Just before serving, take the lid off and boil a few minutes to evaporate more of the liquid.
Spoon into bowls and garnish with a bit of fresh parsley. Makes about 4 servings.