Cut a small amount off the bottom of the onions to ensure they will stand upright.
Cut 1/4 down from the top and discard top piece.
Place onions in a large pot of boiling salted water for 20 minutes. Remove and let cool.
In the mean time, cook potatos and carrots separately until tender. (I steam mine, but any method would work just as well.).
Once cooked, let cool slightly and dice up julienned carrots. You should now have tiny little squares.
Preheat Oven to 180 Celsius (350F).
Go back to onions and remove inner layers and any tough outer skin layers, leaving 2 outer layers intact. This can be done with a melon baller, or teaspoon. You may end up with a hole in the bottom - never mind, this won't even be noticed.
Dice up some of the left over onion roughly until you have approximately 1 Tablespoon. Place 1/2 teaspoon into each hollowed out onion.
Mash potato until smooth, and then mix with carrot, coconut milk, curry powder, salt and pepper.
Share potato mix among onions shells until they are full.
Place onions in oven safe dish with lid, cover and cook at 180 Celsius for 20 minutes.
Remove from oven, top onions with diced tomato and bread crumbs.
Place under griller on med-high for 10 minutes or until crumbs brown.