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Peel away the plastic wrap covering the black pudding. Do not slice it or remove the skin. With the casing damaged or removed the sausage would absorb water and become soggy. Take care not to break the skin casing when removing the outer plastic. Fill a stock pot with water and heat it until it comes to a boil. You can also use a deep pan to simmer the black pudding, though this will take longer and require regular turning. The pot or pan you use should be big enough to hold the entire pudding. Simmering will work best with thinner sausages. The bulky girth of thick sausages makes heating them in a pan impractical. Carefully place the black pudding into the boiling water. It will submerge when placed in a stock pot. If you've chosen to simmer the pudding in a pan, you will need to turn it every few minutes to make sure it gets cooked through. Turn simmering sausages using long-handled tongs to keep from burning yourself. Boiling sausages will need to be checked periodically to ensure that the skin hasn't ruptured. If it has, remove the black pudding from the water immediately, slice and finish cooking on a skillet or in the oven to salvage the flavor and texture of the sausage. Allow the pudding to boil or simmer for 6-8 minutes. You can test the consistency of the sausage as it cooks by squeezing it lightly with a pair of tongs. Once most of its firmness has given way and it has taken on a soft texture, it is ready to serve. Thicker sausages may need to be cooked longer in order to be a consistent temperature throughout.
Remove the plastic wrapping from the black pudding. Bring a large pot of water to a boil. Put in the pudding whole. Heat for 6-8 minutes. Finished.