Preheat oven to 375°F Cut pumpkin in half and remove seeds. Place cut side down on baking sheet. Bake about 45 minutes or until tender but not mush. Flesh should be firm enough to cut into 1/2 inch cubes or slices. Sprinkle with the salt and pepper
Bring 1 cup of stock to boil in saucepan and cook onions in it uncovered until tender over moderate heat. When most of the liquid is evaporated, sprinkle the onions with the sugar and cook until they start to caramelize.
Add the vinegar and remaining stock and continue to cook until they are a deep golden brown but not burned. Add water if the mix seems dry.
The onions should end up in a sweet and sour syrup. Toss the cubes with the onion mix and stir to coat. Sprinkle with the mint [or parsley]