Hamantaschen just wouldn't pinch and hold tight I made a pretty simple and easy hamantaschen recipe last night, and it came out really well. The only substitution I made was to flex 3 eggs for 3 tablespoons milled, gelled flax seed in 9 tablespoons water. I am essentially unfamiliar with the dough, and wasn't sure what to expect. It had a great crumb, shortbread texture, but I ran into the dough unfolding/unpinching while baking.

The dough was good to work with, streched well and didn't break apart. However, it was very dry. Two main problems that may have stemmed from this were that the pockets wouldn't pinch at the edges, and when I left them to cool they dried out very quickly. In the second batch I tried moistening the edges with water to see if it would help glue them together, but to no avail. In the third the dough was becoming very inflexible and I used some canola oil to loosen it back up, but this did little to help.

As it is spoken of as a stiff dough (the author recommends chilling dough overnight), the dryness of the dough itself may not have inherently been a problem. Also, whereas the author says to "mix" the five and a half cups of flour with the liquids, I found I needed to fold cup by cup then knead toward the four cup mark, ultimately shorting the recipe by a half cup of flour. Since the drying out while cooling had no actual affect on the dough (in terms of taste, texture), I am mostly concerned about why the pockets ended up flat upon baking in many cases, instead of little pockets of plum preserves. 

With a dough and recipe like this, what could I have done to ensure better pinches?


Is the amount of baking powder appropriate? The recipe didn't call for any salt, but I added some for flavor; could this have been problematic in causing over-rising?
The flax egg substitution would have had an equal amount of moisture to the egg, but would it have caused such dryness while mixing? The dough results were good in taste, just not structure.
Could over-kneading have been the problem; does too much kneading inhibit flour's ability to adhere to itself?
I do not typically use oil only doughs due to their dryer results, would subbing/splicing some heavier fats or apple sauce have improved the sticking?
Doubtless from the image above, I have not formed these before. Could my pinching technique have been to blame? Is there a secret to it? I have also seen them folded; does folding the corners yield sharper edges than pinching?
It seems Hamantaschen cookies unfolding and leaking is not an uncommon problem. Of course the flax egg substitution can very likely also contribute to the unfolding but here are some tips from someone who has been baking Hamantaschen cookies for a while.

Tips for Creating Perfect Hamantaschen


  1) Find a great dough recipe. Often, the problems people have with
  baking hamantaschen can be traced to an inferior dough. Here are two
  foolproof, tasty dough recipes that I highly recommend. They are easy
  to handle and shape, and they provide great results when baked:
  
  Dairy Free Hamantaschen Dough
  
  Buttery Hamantaschen Dough


Of course you can use your flax egg substituted in for the eggs that the recipes ask for.


  2) Roll your dough out to 1/8 inch thick (or less). You want your
  dough to be as thin as possible, while still being thick enough to
  maintain the cookie’s structure. 1/8 inch seems to be the magic
  number; sometimes I roll mine out even thinner than that. For a more
  doughy texture you can roll it thicker, but remember– the thicker the
  dough is, the harder it will be to handle and shape. Thick dough is
  also more prone to opening/spreading in the oven.
  
  3) Use a thick filling that won’t run/weep from the cookies while
  baking. Knowing the proper consistency of a hamantaschen filling takes
  experience, because each type of filling is slightly different.
  Poppyseed filling has a very different texture than fruit filling, for
  example. A good filling should be somewhat thick so that it doesn’t
  run. 
  
  4) Cut your hamantaschen dough in 3-inch circles (or larger) before
  filling and folding into triangles. Anything smaller than 3 inches
  will be difficult to fold around your chosen filling.
  
  5) Most fillings can be chilled before using to fill hamantaschen.
  I’ve found that fruit, poppy seed, and cream cheese-based fillings
  tend to be easier to work with when they’re chilled in the
  refrigerator. The chilling process thickens the fillings and makes
  them less sticky, which makes them easier to handle with when you’re
  assembling your hamantaschen. Not all fillings are helped by
  refrigeration, however– particularly chocolate-based fillings like
  Nutella, which will harden with prolonged refrigeration. Check your
  filling recipe to see if refrigeration is recommended.
  
  6) Do not overfill your hamantaschen. Use 1 teaspoon of filling per
  hamantaschen cookie. Do not use more than 1 teaspoon. However tempting
  it might be to put lots of delicious filling in the middle of your
  cookie, using more than 1 teaspoon can cause your hamantaschen to
  spread open and leak in the oven. 1 teaspoon is plenty, especially
  when you cut your dough circles to 3 inches… it’s the perfect amount
  of filling.
  
  7) Fold your triangles the right way! Using the proper folding method
  will help your hamantschen hold together and create a beautiful shape.




Please that the sides are folded down so that each "side" has an "end" that is above and an "end" that is below in the fashion of folding the top of a box. This will help in preventing the cookies from unfolding.

Also note in Step 5, to pinch each of the 3 corners gently but firmly.

Source: http://theshiksa.com/2012/03/01/how-to-make-perfect-hamantaschen/