Melt butter in a large skillet over medium heat. Add scallions and sauté until soft, about 3 minutes. Add corn and sauté 1 minute to heat through (or slightly longer if using frozen corn). Add flour and stir to coat corn and scallions. Add milk and bring to a simmer.
Reduce heat to low and cook, uncovered, until mixture thickens, about 8 to 10 minutes. Season to taste with salt and pepper. Yields about 1/2 cup per serving.