This is a recipe from my mother, who got it from her mother. To me it's more like a cake than a pudding, but hey, who am I to question my mother. It was and still is a summertime favorite when blueberries are in season. The original recipe called for Huckleberries. We could not always or rarely find them, so mother used the blueberries. When I was young, I would eat this for breakfast. The hard sauce sounds a little unusual with the vinegar, give it a try. You will be pleasantly surprised. I have given the exact recipe that was in my mother's manuscript cookbook. However I use up to 2 quarts of blueberries and closer to 1 teaspoon of freshly grated nutmeg. The original hard sauce recipe called for a good lump of butter, I calculated that to 2 tablespoons.