One of my favorite pies is Impossible Pie, named such because you need only mix the ingredients and bake in a greased pan and it will form three layers (bottom crust, middle custard, top crunchy coconut) on its own. I found it in an old 50's cookbook:

  • 4 eggs
  • 1/2 cup butter
  • 1/2 cup flour
  • 1 cup sugar
  • 1 cup shredded coconut
  • 2 cups milk
  • 2 tsp. vanilla extract
  • pinch nutmeg
  • zest from a full lemon
  • juice from a half lemon

Mix together thoroughly, pour in a greased pie pan (I reserve about 10% of the butter for this), bake at 350 for 1 hour on top of a baking sheet to catch possible spillover. Rest with a dish towel atop for 1 hour before refrigerating. Best served cold, I would wait at least 12 hours in the fridge.

I've made this before with 3/4 cup sugar instead of 1 cup, and it turns out more or less the same. I couldn't discern the two from looks or texture. But I tried earlier today with 2/3 cup sugar instead and the bottom crust didn't really form. It looks almost like it wasn't cooked enough but I followed the recipe the same otherwise.

I hope it's not too naive of a question, but what does less sugar (with nothing to replace it) do in a pie or cake? The only variable here I changed was the sugar, so I'm assuming that's why it didn't turn out properly.


2 Answers 2


The general answer is yes, in baked goods sugar does more than just add sweetness. Via the Maillard reaction it will contribute to browning and add a more complex flavor than just sweetness in the crust or exterior of a cake or pie. This is one reason why malted barley is added to bread flour and malt or molasses is added to bagle boiling water.

It also interacts with ingredients like eggs and cream and butter which could all influence the characteristics of the custard that you mention is supposed to constitute the middle layer.

That said I don't know enough about this cake to say for sure if 2/3 vs. 3/4 cup sugar could be the difference between success and failure but it seems unlikely. You're talking about 5.3 vs. 6 ounces by volume. That could be the difference between levelling your measuring cup or not.

On the other hand, crust formation is exactly an area where I would expect the sugar to assist, so it is also not impossible that the lower amount contributed to your disappointing result.

The only way to know for sure is to repeat the experiment in controlled conditions and compare side by side!

  • "the difference between levelling your measuring cup and not" can definitely affect how baked goods come out. That is ~12% less sugar.
    – Esther
    Commented Jan 30, 2023 at 19:36
  • I mean, I certainly don't disagree, I just am skeptical that it would mean the difference between total success and total failure here, unless there really is something "magical" going on where it emulsifies at a very specific sugar %. Commented Jan 30, 2023 at 19:41
  • 1
    @PeterMoore it doesn't have to be very specific, just that the transition is in that range - after all, ¾ and 1 cup behaved the same. But it's also perfectly likely that something else changed at the same time, either causing the difference or contributing to it - for example the size of the eggs or the lemon
    – Chris H
    Commented Jan 31, 2023 at 10:33

Sugar tends to create a more "crumbly" texture by breaking up the gluten in a dough, preventing it from becoming elastic. That is likely the source of your issue.

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