Isernio's suggests the following fool-proof method of cooking sausage links properly every time, which does not rob the sausage of taste or texture, and allows it to be finished in a pan, oven or on a grill:
Bring a skillet of water large enough to immerse your sausages, to a boil. Lower uncooked sausages into boiling water, place the lid on and immediately turn heat off. Let sausages sit in the hot water for approximately 7 minutes. Drain the water and wipe out the skillet, if you’re using the same skillet to brown the sausages. This method will guarantee the inside of your sausages will be cooked, when pan browning or grilling. Pan brown, grill or immediately submerge in an ice bath (bowl filled with ice & water) to halt cooking and store in zip lock bags in the refrigerator. For a quick meal, simply brown on each side in an oiled skillet.
Click here for a video of Frank showing you how to cook sausages using this method.
To cook our bulk sausage or sausage taken out of the casing: Either form into a patty (about ½” in thickness) and pan-fry over medium heat in a small amount of olive oil, or crumble the sausage into a pan and cook over medium heat, breaking up with a wooden spoon, until sausage is no longer pink inside.
Pork sausages should reach a final internal temperature of 155°F and chicken sausages should reach a final internal temperature of 165°F. For maximum juiciness do not overcook; use a meat thermometer to take temperature readings.