Broccoli with Mustard Sauce

½ cup chicken stock (or water)
½ tsp dried thyme (or a couple sprigs fresh)
3 cups broccoli florets
½ cup sour cream
2 tsp flour
2 tsp Dijon-type mustard

Bring broth and thyme to boil over high heat. Add broccoli, return to boil, and simmer covered for about 5 minutes until tender-crisp. Remove broccoli, retaining cooking liquid. Blend together sour cream, flour, and mustard and add to liquid. Cook over medium heat until thickened about two minutes, stirring. Stir in broccoli and serve.