Put the potatoes in a pot, cover with water and season with salt and a dash of the vinegar. Bring the pot to a boil, then turn the heat off and allow to sit 10 minutes.
Remove the potatoes and allow to cool, then cut in half or crush lightly if small to make them easy to brown and crisp.
Cut the blood sausage into 1 inch coins. Heat the lard or oil in a large cast iron or similar skillet until lightly smoking, then add the potatoes and cook until golden and crisp.
Move the potatoes to one side of the pan and add the blood sausage coins, cook until crisp, toss the pan, cook for a few minutes more until the sausages are nicely browned, then turn the heat off, toss in the cilantro and green onions, double check the seasoning for salt, adjust as needed, then serve.(The vinegar is optional, but helps enhance the crispness of the potatoes)
