Mix flour, broth, sugar, soy sauce and fish sauce in a small bowl until sugar and flour dissolve. Put aside.
Cook steak strips in wok or large skillet over medium-high heat until browned.
Add broth mixture and the rest of the ingredients. Stir to coat beef and broccoli with the sauce. Bring to a boil then reduce to a simmer. Cook until sauce thickens slightly, stirring occasionally.