Help with croissant

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I have launched myself on a croissant quest.  I am trying to use Ester McManus' recipe out of a Julia Child's Baking with Julie book.  I find she uses 4 1/2 sticks of butter (18oz)  with 18 oz  of flour.  According to what I have read you need roughly a ratio of 1 part butter to 2 parts flour.  Does this recipe contain an error??

You are referrig to the entire butter to flour weight since there is butter in the dough and between the dough. A typical recipe calls for 500g flour and 50-100g of butter in the dough depending on whether you use eggs and / milk in the dough. Then the slab is about 200-250g so it really depends on the recipe but generally thats about right. Some bakers like less butter some like more so it depends on your own experience and preference., also consider the fact that the dough is more like a brioche and requires a lot of yeast to combat the fat and high sugar so if you like to work with fast acting yeast then less butter is probavly preferable - if you like to take it slow then go on the high end (its really a matter of finding a recipe that works for you)