Could you make the batter a day in advance and refrigerate overnight?
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The recipe does not have any leavening, so the usual objection to holding a batter is null. The sweet potatoes are cooked, so they will not discolor. Making it ahead should work. My only question would be for the flour -- it might absorb the liquid content overnight, and possibly would need a little bit more liquid before using. I would try adding in everything else except the flour, and add it just before using. I'd have it sitting out premeasured, so that step is done too -- just mix and cook.