Grilled Clams with a Herb Butter

I saw this recipe on Epicurious and thought it'd be a nice appetizer.  We made it this past week and it was a hit!  We had to grill the clams a little longer than the original recipe called for but it's easy to tell when they are done - just pull them off once they open up.  This would be a nice app for guests!
The recipe called for scallions and I don't like them.  We used a white onion but next time, I think we'll try a shallot and garlic.

Ingredients
1/2 cup (1 stick) butter, at room temp
1 tbsp chopped flat leaf parsley
1 tbsp chopped fresh dill
1 tbsp chopped scallion
1 tbsp fresh lemon juice
Kosher salt & fresh pepper
24 littleneck clams, scrubbed

Directions
Mix first 5 ingredients in a medium bowl until blended.  Season with Salt and Pepper
Heat gas grill to high (or charcoal to a medium hot fire).  Place clams on grill rack (I used a grill pan) & cover with the lid.  Grill clams until they open up.  It took mine probably 10-11 minutes.  Use tongs to transfer to platter or bowl
Dot clams with herb butter & let stand until butter melts.
Serve warm