In a blender add the 16oz can of guava shells and blend until smooth. Add in the lemon juice and blend until combined.
Pour the guava mixture into a small sauce pot and cook on medium to medium low heat for 20-25 minutes. The guava mixture will darken a little bit as the sugars and fruit combine turning into a beautiful filling. Stir occasionally to prevent burning and sticking. Take off heat and let mixture cool completely before using.
Rough Puff Pastry Dough
In a large bowl whisk together the flour, sugar and salt. Add the cold cubed butter on top of the flour. Using your hands gently mix the butter into the flour. Do not break the butter down just start to incorporate the butter into the flour. (See video above)
Begin adding ice cold water 1 tablespoon at a time. The flour will begin to look "shaggy" and crumbly. Do not break down the butter.
By the 5th tablespoon of water the flour should start to get moist enough and begin coming together like dough. Again, do not break down the butter, keep the butter in chunks but still incorporate. (Keep referring to the video if needed.)
If at any time the butter begins to feel too soft put the mixture back into the refrigerator for 5-10 minutes. Once all of the water has been added dump dough onto a floured surface. Mold the dough into a 5"x8" rectangle. Fold the dough into thirds like a business letter. Wrap tightly with plastic wrap and place into a tightly sealed container. Put into the refrigerator for 2 hours. You can leave the dough like this for up to 24 hours. I have done this first part in the morning and left it until the evening for fresh pastelitos for dessert.
After at least 2 hours remove the dough from the refrigerator to a well floured surface. The dough is going to be rolled and folded for a total of 6 times. Begin rolling the dough out with a rolling pin. Roll it until you make a 6"x12" rectangle. Fold the dough again like a business letter. Turn the dough clockwise or a 1/4 turn once and begin rolling out until you get another 6"x12" rectangle. Fold the dough like a business letter for the second time. Each time you fold the dough turn it a 1/4 turn. Continue the process for a total of 6 times. (Refer to the above video if needed.)
Fold the dough again like a business letter. Turn the dough clockwise or a 1/4 turn once and begin rolling out until you get another 6"x12" rectangle. Fold the dough like a business letter for the second time. Each time you fold the dough turn it a 1/4 turn. Continue the process for a total of 6 times. (Refer to the above video if needed.)
After 6 rolls and folds wrap the dough tightly in plastic wrap again and place in a sealed container in the refrigerator for 15 minutes. Again, it can be left for another 24 hours if you need to. At this point you can also freeze the dough for up to one month. If frozen when you are ready to use let it thaw in the refrigerator before using. After 15 minutes remove from refrigerator and the dough is ready for use.
Pastelitos de Guayaba (Guava Pastries)
Preheat oven to 350 degrees. In 2 small bowls prepare egg wash and corn syrup mixture. Roll out pastry dough onto parchment paper. Cut pastry dough into 3"x3" squares.
Using a pastry brush, brush all sides of bottom squares with beaten egg wash. Put a spoonful of cooled guava mixture onto each bottom square. Cover each bottom square with top square of pastry dough. Using a fork seal the edges using the tines of the fork.
Brush each pastry with egg wash and make a slit in the top for venting. Put pastries with the parchment paper onto a baking sheet. Put baking sheet into the refrigerator for 10 minutes. To keep flaky layers the dough must always be cold. If the butter melts while handling the layers will disappear.
After 10 minutes remove pastries from the refrigerator and bake for 25 minutes. After 25 minutes quickly brush the top of pastries with corn syrup mixture and sprinkle with Christmas colored sugar crystals. Continue baking for 5-10 minutes until golden brown.