Fill a medium saucepan with water. Leave enough room to add the shrimp.
Stir in the salt, squeeze half a lemon, then drop the squeezed lemon into the water. Add peppercorns and parsley here if you want.
Bring the water to a rolling boil over high heat, then turn off the heat and let the water stop boiling.
Add the shrimp to the hot water, give a quick stir, cover the saucepan, and let the shrimp poach for 4-5 minutes until they turn opaque.