In a large mixing bowl, combine the fresh pig's blood, diced pork fat or beef suet, finely chopped onion, rolled oats, and barley.
Add the milk, salt, ground black pepper, ground allspice, dried thyme, and dried sage to the mixture.
Stir well to combine all the ingredients thoroughly.
Transfer the mixture to a large pot and cook over medium heat, stirring constantly, until the mixture thickens and the oats and barley are cooked, about 15-20 minutes.
If using natural sausage casings, stuff the cooked mixture into the casings and tie the ends securely. Alternatively, you can shape the mixture into patties or press it into a loaf pan.
Allow the black pudding to cool completely.
Once cooled, slice into rounds or desired shapes.
Heat a little oil in a skillet over medium heat.
Fry the slices of black pudding until they are crispy and heated through, about 2-3 minutes per side.
Enjoy your meal!