Add salt. Squeeze the juice of the lemon into the pot and add the peel and flesh once squeezed. Add the peppercorns, parsley, salt, and bay leaf..
Bring the pot to a rapid boil over high heat. Reduce heat and simmer for ten minutes.
Remove from the heat.
Add the shrimp. Stir. Put the lid on the saucepan. Cover the pot. Let sit for 4 minutes, until shrimp are opaque, pink, and semi-firm.
Meanwhile, prepare an ice bath: In a large bowl put two cups of ice cubes and fill halfway with cold water.
When shrimp are cooked, drain off the hot liquid and transfer shrimp (but not the aromatics) to the ice bath. Let them sit in there for a few minutes to fully cool off before draining.
Peel and use in shrimp cocktail or in salads (or wherever you might want to use cooked, chilled shrimp).