Cook pork heads in boiling water (100°C / 212°F) for 100-110 minutes. Cook pork rinds in boiling water (100°C / 212°F) for 35 minutes until tender. Once cooled, peel and cut the pork head meat into 3 cm x 3 cm pieces and the fatty parts into 1 cm x 1 cm pieces. Peel and cut the onion into eighths.
Grind the cooked pork rinds and onion using a 2 mm perforated grinding disc. While grinding, pour the hot broth through the grinder and mix with the ground rind mixture. Add the blood and mix well. Add the diced head meat (reheated in the broth), then add the salt, black pepper, suar, marjoram, ground allspice, cinnamon, and finely grated garlic. Mix everything thoroughly until well combined.
Fill the mixture into casings (such as stomach or sterile intestines) or containers (such as cans or glasses). If using casings, heat in water at 85°C (185°F) for 1 minute per millimeter of thickness. If using cans or glasses, cook in boiling water (100°C / 212°F) for 2 hours.
Cool the cooked sausages in an ice water bath until fully cooled. If using natural casings, shape by placing between a board and weights. If desired, cold smoke the sausages for approximately 2 smoking sessions.