Grilled sweet potatoes with balsamic glaze

1. Scrub sweet potatotes well.
2. Place in a large pot and cover with cold water.
3. Bring water to a boil, reduce heat, and simmer until almost tender, about 40 minutes (they should be a little undercooked).
4. Remove from heat and drain; peel and set aside.
5. (sweet potatoes can be prepared 1 day in advance up to this point).
6. combine balsamic vinegar and sugar in a small saucepan over high heat.
7. Simmeri mixture until it is thick and syrupy, or reduced by one-half, about 10 minutes.
8. Remove from heat, add butter and cool.
9. if using grill, heat grill to high.
10. Cut sweet potatoes crosswise into ½-inch-thick slices.
11. Brush tops of slices with oil and place, brushed side down, on grill until marked, about 2 minutes.
12. While slices are cooking, brush the other sides with remaining oil and turn over.
13. Grilli until marked, about 2 more minutes.
14. Brush grilled sweet potatoes on both sides with vinegar glaze and serve.
15. if using broiler, heat broiler to high.
16. Arrange sweet potatoe slices on a baking sheet and brush tops with glaze; no oil is necessary.
17. Place baking sheet under broiler and broil until glaze starts to bubble, 3 to 4 minutes.
18. Remove from oven, turn potatoes over, and brush with glaze.
19. Broili for 3 to 4 more minutes.
20. recipe by : martha stewart living november 1994.