Blanch broccoli in 6 quarts of boiling salted water. (About 1 tbsp salt.), uncovered, 2 minutes, then drain in a colander. Immediately plunge colander with broccoli into an ice bath to stop cooking, then drain again. Spread broccoli out on a kitchen towel to dry. (Broccoli will still be crisp.)
With motor of a food processor running, drop garlic through feed tube and process until finely chopped. Add remaining ingredients (except broccoli)and a 1/2 tsp salt and puree until smooth. Serve broccoli with dip.
NOTE: Broccoli can be cooked 1 day ahead and chilled in a sealed bag. Dip can be made 2 days ahead and chilled, covered. Bring to room temperature before serving.