Prepare the poaching liquid: fill a small stockpot with water, add 1/2 onion (whole), parsley, peppercorns, bay leaf, and lemon/ squeeze the liquid from the lemon into the stockpot and throw the entire lemons into the water as well. Bring to a boil, season generously with salt (I use at least 1 tsp), reduce heat and simmer for 10-15 minutes. Return to a rolling boil, add shrimp, cover pot, remove from heat, let stand until shrimp are cooked through about 3-4 minutes. Shrimp are cooked when they are pink, curled up, and no longer opaque.
Make the salad
Remove the shrimp from the poaching liquid and chop into bite size pieces. Add to a bowl and immediately toss with scallions, olive oil, and salt. The shrimp should still be warm when you toss with the olive oil. Add vinegar if desired.
Place in the refrigerator and allow to chill. Serve with lemon wedges.
Will keep for 3-4 days in the refrigerator.
Why is vinegar optional:This is a highly debated topic in my family. My grandfather always added a touch of vinegar but I tend to like it with just olive oil. The trick is that you have to use really good olive oil!Try a small amount with vinegar and see if you like it!