Heat 2 tablespoons of olive oil in a medium skillet over medium-high heat. Add the chopped onion and cook, stirring frequently, until softened and browned—about 10 minutes.
In a large pot, heat the remaining 2 tablespoons of olive oil over medium-high heat. Add the pork shoulder, season with salt and pepper, and brown on all sides—about 3 minutes.
Add the cooked onion, bay leaves, water, and vinegar to the pot. Raise the heat to high and bring the mixture to a boil. Once boiling, reduce the heat to low, cover, and simmer for about 45 minutes, or until the pork is tender.
Meanwhile, ensure the pork blood is fully liquified. If using coagulated blood, blend it with 1 cup of water until smooth. Strain through a fine mesh strainer to remove any solids.
Add the strained pork blood to the soup and simmer, uncovered, for at least 15 more minutes to allow flavors to meld.
Serve hot, ideally with hearty bread or traditional flatbreads.
Keyword Ancient Greek pork soup, High-protein ancient soup, Historical Greek recipes, Pork blood stew from Sparta, Spartan black broth recipe, Traditional Melas Zomos, Warrior’s broth recipe