Mustard seeds are listed twice in the recipe. Should some be ground and some be left whole? Or is this a typo? Thank you for your help!

Very sorry about all the confusion. I've been having a devil of a time trying to edit the recipe -- it just never seems to change!

The correct amount is 1 tablespoon. I just leave them whole, but you could crush them a bit in a mortar and pestle if you want more mustard flavor. I would not use ground, however, as I think that would be too strong and would probably also leave a film on the celery.

In the headnotes to the recipe, the tester says that she used 1.5 tsp as a compromise and liked the results. You might try that!