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I am making traditional german lebkuchen, and it requires for it to cool over night in the fridge. My mom suggested that i freeze it for a few hours instead, but beng the science-fueled person that i am, i need to know: Will the same thing happen if its frozen.

for those who dont know, when cookies are cooled in the fridge overnight the solids and liquids in the mixture have more chance to make a reaction and therefore make wonderful cookie.

Here is the recipe.

http://allrecipes.com/recipe/german-lebkuchen/

should it work the same way? How long should i freeze it for?

You could freeze it, but it might affect the flavour, texture, colour, well the whole cookie really. But it wont be the same as leaving it in the fridge all night. You'll just be preserving it as it is without letting it do what it does in the fridge.

Often if something is meant to rest overnight, it's often because said thing will not be at it's most flavourful, tenderness, moist/juiciest. Just like with wine, it can take ages for a full bodied and flavourful wine to be produced. It just takes patience.