Melt 1 tablespoon of butter in a skillet. Add cracker crumbs and cook over medium heat, stirring, until lightly browned. Remove to a plate and set aside.
Melt 2 tablespoons of butter in the same skillet. Add the finely chopped onion and cook, stirring, until tender. Stir in the flour, salt, dry mustard, and pepper. Cook, stirring constantly, until mixture is hot and bubbly.
Whisk together the milk and egg. Gradually add the milk mixture to the skillet, stirring constantly. Cook, stirring, until mixture is thickened and begins to boil. Add the drained corn. Cook until heated through. Spoon into a serving dish and sprinkle with the browned cracker crumbs.
Calories per serving: 162
Fat per serving: 8.2