I have always known that the day after Christmas is Boxing Day in the UK, Australia, and other Commonwealth nations; what I didn't know was what that meant. Honestly, I despise that sport, so I never took the time to read up on the holiday.
Cube sweet potatoes, boil in salted water until tender (about 20 minutes).
While the sweet potatoes are cooking, melt 2 T butter in large frying pan.
Sauté garlic in butter until tender over medium heat. Add ground beef and sauté until no longer pink. Season with salt, pepper, ground cumin, and ground curry powder. Add balsamic vinegar. Add tomato sauce and cook, uncovered, over low heat for 10 minutes, adding more tomato sauce as necessary to keep moist.
Add the vegetables after the meat has initially cooked. And cook till fork tender.
Mash sweet potatoes in bowl with remaining butter, season to taste.
Place beef mixture in a baking dish. spread mashed sweet potatoes on top, making rough peaks with a fork so that there are peaks that will brown nicely. You can use the fork to make some designs in the potatoes as well.
Cook in 400 degree oven until bubbling and brown (about 30 minutes). Broil for last few minutes if necessary to brown some more.