Preaheat the oven to 400°F Grease an 8-inch square baking dish. Using a food processor, puree 1 cup corn.
In a large nonstick skillet, heat the oil over medium-high heat. Add the onion and cook, stirring occasionally, until softened, about 5 minutes. Stir in the remaining 1 cup corn and cook until the corn begins to brown, about 5 minutes. Stir in the chorizo.
In a large bowl, beat the eggs. Stir in the milk, pureed corn and tortilla crumbs. Add the onion-chorizo mixture and season with salt and pepper. Transfer the mixture to the prepared pan and bake until set and a knife inserted in the center comes out clean, about 25 minutes; let sit for 10 minutes. Sprinkle with the scallions.