Toss peeled shrimp with salt & baking soda in a large bowl. Let rest for at least 10 minutes, or refrigerate uncovered for up to an hour.
Heat 3 T. olive oil in a large skillet over medium heat. Cook shrimp in single-layer batches, turning each over when the bottom is opaque, then transferring to a plate.
Reduce heat to low and add remaining olive oil, pepper flakes, and garlic. Cook until garlic is light golden, about a minute.
Add white wine and cook, scraping any browned bits off the bottom, until wine is reduced by about half.
Add butter and swirl to melt. Add lemon juice & salt and bring to a simmer, stirring constantly so the sauce is smooth.
Return shrimp to the skillet with fresh parsley. Toss to coat in sauce, then remove from heat once shrimp are warmed through.
Serve hot with a crusty baguette or over pasta.