In honesty, the easiest way to get 3240kcal would be by having here together. Butter and bread together.
Not sure where bread came from, though. I wouldn't suggest anyone eat bread. Thought this was about carbs in general.
Of course hunger signals come differently. 3240kcal of white potatoes would be a hell of a lot harder to get down my throat than 3240kcal of butter. Would keep me full for longer, too.