1 ½ pounds large shrimp, peeled and deveined or shell-on
Kosher salt
3 tablespoons unsalted butter, cold and cubed
1 tablespoon hot sauce, plus more to taste
2 tablespoons neutral oil (like vegetable or grapeseed), plus more as needed
6 scallions, trimmed, white and green parts cut crosswise into 1-inch segments
Pat the shrimp dry and season with 1 teaspoon salt. Put the butter and hot sauce in a large bowl.
Heat the oil in a large (12-inch) cast-iron skillet over high. Add the scallions and cook until softened and browned in spots, 1 to 2 minutes. Transfer the scallions to the bowl with the butter and hot sauce.
Add the shrimp to the skillet in a single layer and cook, undisturbed, until golden brown, 2 to 3 minutes, adding more oil if the pan is dry. Flip and cook until opaque all the way through, 1 to 2 minutes more.
Transfer the shrimp and any juices to the butter, hot sauce and scallions. Toss vigorously until the butter is melted and the shrimp is glossy. Taste, and add more hot sauce and salt as needed.