Cut off stems of broccoli; set aside for another use such as soup.
Divide tops of broccoli into florets.
Steam the florets for 5 to 7 minutes, until crisp tender.
Rinse under cold water and chill for an hour or several hours.
Combine yogurt with remaining ingredients and refrigerate.
To serve, arrange broccoli on shallow serving plate and pour yogurt dressing over.
NOTE TO COOK: Carry broccoli and dressing separately to party and combine at party.