4 medium sweet potatoes, peeled (2 pounds)
1 cup water
1/3 cup Dijon Mustard
2 tablespoons olive oil
1 tablespoon fresh rosemary, minced (or 1 teaspoon dried)
1/2 teaspoon salt
1/4 teaspoon pepper

Cut potatoes diagonally into ½ inch-thick slices. 
Place potatoes and water in a shallow, microwave-safe dish.
Cover with vented plastic wrap.
Microwave on high for 6 minutes or until potatoes are crisp-tender, rearranging once. 
If necessary, cook potatoes in two batches.   Drain well.

In a bowl, combine mustard, oil rosemary, salt and pepper.
Brush on potato slices.  Place potatoes on a greased rack.  

Grill over medium-high heat for 5 to 8 minutes.