In a medium skillet, cook onion, thyme, and rosemary in olive oil until lemon juice almost has evaporated.
Stir in the 1 cup chicken stock or broth; boil mixture about 4 minutes or until reduced to about half. Stir in pepper.
In a small bowl, stir together the 1 tablespoon chicken stock or broth and cornstarch. Stir into sauce. Cook and stir until thickened and bubbly; cook and stir 2 minutes more. Makes 3/4 cup.