Cut kernels from 3 ears of husked corn and place in a medium bowl. Using the back of a chef’s knife, scrape milk from cobs into the bowl; discard cobs. Heat 1 Tbsp. oil in a medium saucepan over medium. Cook 2 oz. smoked Spanish chorizo, finely chopped, stirring occasionally, until it starts to get crisp, about 2 minutes. Carefully pour chorizo oil into a small bowl (use a slotted spoon to hold back chorizo); set chorizo oil aside. Return chorizo pan to medium heat and add 12 scallions, white and pale green parts only, thinly sliced, 4 garlic cloves, thinly sliced, ½–1 serrano chile (depending on heat), finely chopped, 1 Tbsp. olive oil, and ¾ tsp. salt. Cook, stirring occasionally, until vegetables are softened but not browned, about 2 minutes. Add corn kernels and cook, stirring occasionally, until bright yellow and softened, 5–7 minutes. Remove from heat and let corn mixture cool in pan 5 minutes. Gently mix in 1 cup buttermilk and ⅓ cup chopped cilantro. Taste and season with more salt if needed. Season 12 large sea scallops (about 1 lb.), side muscle removed, patted dry generously with salt. Heat reserved chorizo oil and 1 Tbsp. olive oil in a large skillet over medium-high until just beginning to smoke. Cook scallops on one side, reducing heat if they are taking on too much color and moving around in pan for even browning, until a golden brown crust forms on the bottom, about 3 minutes. Reduce heat to medium-low and turn scallops over. Add 2 Tbsp. unsalted to skillet and, using a spoon, baste scallops with butter 30 seconds. Transfer scallops to a plate. Squeeze halved lime over. Divide corn mixture among plates and arrange scallops on top. Serve with lime wedges for squeezing over.