2 large portabella mushrooms
1/4 onion, chopped
1 teaspoon garlic, minced
1-1/2 teaspoon olive oil
2 teaspoons gf
worcestershire sauceSalt and freshly ground black pepper
2 Tablespoons balsamic vinegar
3/4 cup fresh spinach, 1/4 cup finely chopped
1/4 teaspoon dried tarragon
1/2 cup heavy cream
1/2 teaspoon cornstarch
1 Tablespoon gf stone ground mustard